Reliability is an issue for me, but in my workstation I need speed more than I need five 9's. So I have a Vertex 2 and a 750Gb HDD in the DVD space using an OptiBay [1]. Time Machine backs up the SSD to the HDD with room to spare. I have a bunch of "old" disks that I can drop in and start using immediately (the HDD in the bay is the original boot drive in fact). And all my code is in remote repos if I lose the whole thing. I find I'm regularly (every 9 months or so) upgrading my disk, and in fact the Vertex 2 is probably the longest I've gone without upgrading.

[1] http://www.mcetech.com/optibay/