Intel X25-M or X25-E are the best SSDs right now.
SSDs don't slow down if you fill them up. They degrade with writes, reads, and deletes. Basically if you have it as just a boot drive and not saving all your work to it, it would last a little longer.
We have 7 art machines here at work with the X25-M 80gig G2. After 2 months, they are still working fine. I've got one at home too since the release of the G2 and it's still working fine. I play all my games off my Raptor drives though and I run the Intel optimization utility daily.
The Intel SSDs are the hottest thing on the market right now just below the new ATI HD 5800 series cards. They are releasing a new line of SSDs, X25-X which are suppose to be cheaper, but slower (only 170 mb/s, which is still pretty darn fast)