I've gone through 2 clear speck cases. Hate them. Here's why:
The weight of the shell for the display WILL affect the hinge. At least it did for me, other people may have been lucky. I ended up taking the bottom off my computer to locate the hinges, and there are simply 3 screws on either side. They're tiny torx, but I think I used a 1.5mm flathead. Tightened them all up, BAM! Loose display that's plagued me for so long DONE.
The worst part of the case is the bottom tray. It's attached with 4 little tabs at each corner, and they've all broken off within a month or two. Now with my first case, I figured I wasn't taking very good care of it or whatever, so when I bought my new one, I was very careful in putting the computer in it, and with the daily use as well as removing it about once every 2 weeks to clean all the crap that accumulates between the computer and the case. Still, the tabs broke. My fiancée has a 13" uMB pink speck case on hers and it's been flawless for almost a year (totally jealous). I'm a case-whore, I like things wrapped up and shielded from my most cruel of uses. Sadly, haven't found Speck to stand up. Right now my computer is naked (sans the trackpad/palmrest and Moshi anti-glare screen protector). I'm looking at the matte black ones... It would match my iPhone.
One other thing, that crap that accumulates between the computer and case will actually take little knicks out of the aluminum. Hate that I hated it, cause I really wanted to love the Speck Clear Case for my 15" uMBP. Sadly, I spent $100 on 2 cases that both sucked.
All just my experience, and if someone has a case for the 15" they're raving about I'm certainly all ears...