Honestly man there have been so many problems with these things that if your only gripe is the slanted keys i suggest you stick with the one you have. I am on my fourth AluMB right now. Ive had everything from Blown speakers to a flexed body causing the laptop to wobble significantly on a flat surface.
If you don't have any more severe issues such as problem pixels or a warped body or misaligned lid, etc, just stick with what you have. Stick a business card under the slanted edge of the key and push down on the other end if you really want to have level keys, but if it doesn't affect the functionality of your macbook, I'd say leave it be.