After a summer of general disappointment that's so far only seen Star Trek emerge as a blockbuster to really deliver amidst a sea of mediocrity such as Terminator: Salvation and Wolverine, it seems many have been pinning their hopes on Transformers: Revenge Of The Fallen being the jewel in the 2009 crown. Indeed, after talk of an opening weekend north of $150m, and trailers that promised a bigger, bolder and generally more gung-ho approach, there was a tangible feeling that this could actually be quite good.

But here's the thing - this is Michael Bay, so expectations should always be tempered somewhat. Personally, I was left mixed by 2007's Transformers. Neither the complete disaster I was dreading, nor the ultimate guilty pleasure I was hoping it would be, it fell someway short of what it potentially could have been, and felt too mired in Bay's let's-just-blow-stuff-up-drenched-in-backlight-and-throw-some-comedy-sidekicks-in approach.

So, while I'm sure there'll be many who'll approach Fallen hoping it'll be the action movie they've been waiting for this year, there are no doubt those like me who'll approach it with the please-God hope that it could offer some redemption for the first film's many pitfalls, learn from its mistakes, and provide two hours of solid entertainment.

Yet, even with expectations lowered, and any judgements as to the creative integrity of Michael Bay temporarily put to one side, Fallen makes for a terribly disappointing experience. Which isn't to say there's nothing to enjoy here. Far from it, there are moments of breathtaking technical wizardry that make you long for what could have been, given the right pair of hands at the helm. But this is film-making by numbers, churned out far too quickly on the back of the first film's box office success, and with little consideration of story, character or anything like common sense.

To be honest, it's difficult to know what the story here actually is. If the first film's Allspark felt like quite a clunky MacGuffin, it at least propelled the narrative forward in quite streamlined fashion. The Decepticons wanted it, the good guys had to stop them from getting it - all very simple and effective. Fallen sets itself the task of reuniting all the principal characters from the first film (Jon Voight's Defence Secretary is the one major absentee) and yet can't create a storyline that gives them any real motive or purpose, other than to either run away from something or towards it at various intervals. While stuff blows up.

Sam (Shia LaBeouf) is off to college, and in the process stumbles upon a piece of the all-spark on his old jumper (yes, the film is that dumb) that has him seeing codes and symbols which slowly unravel a mystery; Mikaela (Megan Fox) is stuck working at her dad's garage (Fox gets a suitably Bay-esque lingering intro shot of her bent over a motorbike); Josh Duhamel and Tyrese Gibson's bland soldiers are now part of a not-very-covert special forces team that has humans and Autobots working side-by-side to track down any remaining Decepticons (the film ignores the futility of humans trying to defeat Decepticons with standard weapons - didn't these guys watch the first film?); while Megatron is awoken from his seabed slumber and returns to Cybertron in an attempt to free his master The Fallen, an age-old Decepticon who seems determined to destroy Earth for some reason  If this all sounds a bit hackneyed and confusing, then this is just the start.

There can't be many other directors less concerned with creating a coherent narrative or sense of rhythm than Bay. And so the film has a rather schizophrenic feel to it, jolting awkwardly from comedy to action to melodrama with barely enough time for scenes to play out to a natural conclusion. The first hour jumps back and forth across disparate story strands without pausing for breath. And by the time the film introduces its equivalent Allspark - the Matrix, which somehow unlocks a planet-destroying weapon - we're an hour and a half in, and patience has been well and truly tested.

Of course, much of this could be forgiven had the film delivered on the considerable promise hinted at in the trailers and some truly eye-popping set pieces. And to give the film credit, Fallen's effects are frequently jaw-dropping. The occasional design issue aside (Starscream looks all shoulders and top heavy, Megatron merely a hunk of silver metal), Fallen's gallery of Transformers look quite beautiful at times. Yet Bay still can't manage to give the majority of his robot characters any semblance of character.  Save for Bumblebee and Optimus Prime, two Transformers easily distinguishable by their colour and voice (or lack thereof, in the former's case), it's hard to make out who exactly is who, rendering action scenes oddly flat and unengaging.

Worse, Bay seems completely unconcerned with creating any sense of space or logic to his action scenes. There are three major set pieces of note here, with only one really hitting the mark, a wonderful forest battle between a dual sword-wielding Prime, Megatron and other Decepticons (it's hard to tell, really). The other two - an opening Shanghai skirmish and a climactic desert battle that sees the introduction of the impressive Devastator - never take flight in the way you hope they will. 

Whilst I'm sure there are many who appreciate the Michael Bay oeuvre, you have to acknowledge that here is a director who's refused to develop his visual style since Bad Boys almost 15 years ago. So we get the usual camera circling a couple when they're kissing, slow-motion running away from an explosion, the gratuitous over-extended tracking shot just to prove he's not all about fast cuts and MTV-styling. It makes you long for a director with a real grasp of visual geography, and halfway through Fallen my mind drifted to the thought of a Kathryn Bigelow directed Transformers film and all the pleasures that would reap, however unlikely the match-up.

At the heart of Fallen's problems is the distinct lack of new ideas on show. Screenwriters Roberto Orci, Alex Kurtzman and Ehren Kruger (the latter apparently a lifelong Transformers fan, though you'd hardly tell from the treatment many staples of Transformers lore are given here - step forward the under-developed rivalry between Megatron and Starscream) seem content to borrow liberally from past movies, and not very good ones at that: Alien vs. Predator, Terminator 3, Spider-Man 3 are just some noticeable for their influence. Elsewhere, the film simply recycles parts of 2007's Transformers in the belief that more of the same will do just fine, substituting Anthony Anderson's bumbling techno wizard with Ramon Rodriguez's Leo, or staging a climactic desert battle that seems eerily similar to the first film's Scorpinok attack, albeit with less flair.

Yet for all the negatives, there are some good moments sprinkled throughout Fallen; Prime is given enough screen time to justify a visit for most fans; Bumblebee remains a great comedy foil; Kevin Dunn and Julie White make for an inspired comedy double act as Sam's parents, stealing every scene they're in; while the new Transformers Mudflap and Skids, though blessed with truly awful names, are given some surprisingly funny, if juvenile, lines.

In truth, Fallen makes for a better comedy film than it does an action film. Not quite the outcome many would expect, or would want, but in a film that runs over two and a half hours with very little excitement, it's important to be grateful for small mercies.