I've read a bit about SSDs, written by techie photographers trying to get things running more quickly. They're faster in most cases, but sometimes performance stays about the same. Booting windows is a lot faster, batch processing raw images is about 20-30% faster in Lightroom. One guy on a private forum i'm on had a raid array of six X25 units, the numbers were quite amazing, but that's not really practical or really all that useful yet. For most people I don't see a huge benefit unless you're waiting for the computer a lot - often adding RAM to be used as disk cache can be pretty effective.
I expect i'll move to SSDs in a couple of years for my working files, but I have 200-600GB of working files at a time so it's not time yet. I do a lot of raw image conversion, I suspect a new CPU and DDR3 memory will be needed at the same time as SSDs to remove other bottlenecks.