I really think Mirrors edge was a victim of its own hype/PR machine, and not anything inherently wrong with the game. Having not heard about it till it was released, and salivating once I saw the trailer I really didn't have alot of expectations going in except running and awesome would ensue. In comparison though if you went in expecting certain things from the game (no combat as an example), you probably got run down some.
I mean, I still can't beleive this didn't sell great?! It was literally my favorite game I played since portal and just as good of a deal (payed a discounted price on steam 1-2 months after it came out). It was just totally different from any other game, and thankfully instead of creeping into it they mostly wholeheartedly jumped into how/why it was different. From the amazing visual style (reflective pristine simplicity of outside to the varied interiors), to the slick tricks, to a good sense of urgency it screamed different yet cool immediately. I'll get to the gameplay later, but I didn't have a single problem with it. Once I realized the whole thing was working off of a consistent physics model and the games emphasis was on speed it became a smooth masterpeice of a 6hour chase scene. Not only that for a single player game, you could literally just WATCH someone play it and enjoy it if they were flowing well.
The gameplay was very tight, although I freely admit I sucked horribly at first. I'm one of those people that refuse to get a gamepad for a PC, so it was mouse/keyboard from the get go [although I did bind some stuff to the thumb buttons on the mouse etc]. I really think that made the difference. Not that the game was designed soley for the PC, but the margin for error WAS larger with the increased precision of a mouse. In fact, knowing how everything was when it worked right, I was able to play it on my brother's PS3 without any of the constant dying he had [and once he saw how it was supposed to be played, neither did he]. The big trick was realizing even though you were disoriented and didn't know your way, the game just worked better if you focused on FLOW instead of direction. Sure occasionally your had to stop to look around, but usually it all worked out if you just ran flat out and always went for the high ground. In that sense the red path guides were cruical on a first playthrough (although replays are much better without them). You could be a total noob, partially lost running full tilt and still know where to go at the last second, allowing the proper trick if you were fast enough.
Alot of people also hated the combat but it really fit the mood & story. The combat wasn't an add on, it reinforced the sense of pace (actively with chases at times) to keep you flowing and not slowing down. Your character was not James Bond, nor Bruce Lee; her whole collection of skills involved movement and running. So of course she sucked with a gun mostly, and based on all the tricks you do, of course you had to ditch them fast. Most of the "non-optional" fight parts (where the enemies were outlined in red) were actually skippable if you just moved fast enough or found the right path because you could get shot a few times... Its here that the reality of the game really came up short, but didn't detract from the immersion (and infact the comic style cutscenes helped) because the game infact had a movie/comic feel. At points it really felt like a chase out of the matrix except with more realism in respect to physics. When you did in fact REALLY have to fight, the most effective moves came still relied on speed. A wall-run flying kick was an instant KO, and a sliding balls kick stunned a guard long enough to usually get out of sight. When there were more guards it became a ballet of quick disable [I gave up on timing take downs because it was too slow] --> grab a gun, run up/around to the next and quickly shoot them when you were close ---> drop gun, then flee or pick up next one. Except for 1-2 areas, taking out two key guards was enough for resuming your getaway. MOST importantly, the chase's and combat made the areas without them later in the game really shine. The favorite sequences were: the sewer catwalk climb area & the under construction building climb. They were a bit slower paced, had some puzzle elements, and look absolutely cinematic if run without slowing down or messing up. I came back again and again to time trial these sections, and also to clear some firefight areas without ever touching a guard or slowing.
It just depressed me when I didn't know if this would have a sequal, and I really hope we see more than an iPhone game out of the IP... I remain amazed how different Mirrors Edge and Assassin's Creed were using similar ideas on movement, and I know which one I liked better. Given a longer game, and maybe a proper tutorial and I'm conviced you would have dinamite of a sequal.