As someone who played it and loved it, I'd say the only "mixed" thing about it is that, despite how EXCELLENT the game is, how well it handles, how fun First Person Parkour turned out to be... there's a severe dirth of content to come back and revisit. There's a reason people have been clamoring for years for an expansion/sequel.
tl;dr: Mirror's Edge is worth your money, especially at a discount.
EDIT: AT FIVE DOLLARS IT'S A STEAL, BUY IT DOGBERRY, BUYITBUYITBUYIT.
MIRRRORRRRRR'S EDGE. OMGOMGOMGOMGOMG.