One thing I try to not get sucked in by is the advertisements for games. You'll find that the majority of imagery that they throw up on television for games tends to be the cut scenes and the beginnings and/or endings, cut and mashed together into a 'teaser' sort of trailer thing. Rarely they'll put stuff public as to the actual gameplay, and I think its better to buy magazines or look it up on the internet and see how the game actually plays out. I recently acquired Boktai, thinking it was going to be very Pokemon-like in the way it plays out, but no, it was... I can't explain it. It just wasn't. Even Magi-Nation for the GBC was more similar to Pokemon than Boktai was.
... Actually, I dont even trust magazines. Some of the scores they give for games are retarded. Trust your own judgement of what is a good game. Always do research before you fork out money for something, thats my opinion. Having looked into Mirrors Edge, I'd put it on my buy list. I'm not *desperate* for it, so I'll be waiting for it to come down in price first, I suspect.