For this application, the main flaw (they suck at writes) of the cheaper flash-based SSDs isn't really an issue. Except when you install/patch, which will take longer. For running around Dalaran or whatever, you're talking more or less pure reads - which will work fine on the cheaper drives. I'm using an OCZ model I picked up on sale, no complaints here. It is NOT a hard drive replacement - but it makes a great supplement for multiboxing.

If you don't know how to copy & symlink your data folder yet, the instructions should be around here somewhere.