I just added two generation 1 Intel X25-m 80GB SSD's to my overclocked pc. It had been running XP on C:, XP swap on D:, and PS swap on E:.
I replaced C: with one SSD, and added an F: drive, which has XP swap, PS swap, Bridge cache, and ACR cache.
Timings you might care about:
Boot went from 2:24 to 1:08 (virus, firewall, and Speedfan -used to- take awhile to finish loading). As often noted, you can immediately start opening other programs, without having to wait for Windows to finish loading.
Converting and opening, to PS, ten 11MP raw files with lens corrections, USM, and other tweaks went from :36 to :33.
Starting Bridge went from :09 to :02.
But by far the biggest change is that programs and windows just SNAP open, as if they had already been running. Even surfing has sites opening in 1/4 the time. Installing programs is lightning-fast.
There's great info at anandtech.com, PC Perspective storage forum, and OCZ Technology forum. Use Anand's SSD tests to decide which brand and model to buy.