I put a OCZ Vertex 2 60 Gig SSD in my Toshiba laptop.
It really is fast. Booting is pretty quick, although I don’t do much of that. Chrome and Thunderbird launch quickly although, again, I mostly just leave them running all the time.
Beyond that, I hope it helps battery life, but since I took the machine from Windows 7 to Ubuntu 10.10, I suppose I will never know which change it was that made the difference.
Still, while I have little to no hard evidence to support it, I feel fairly happy with the choice.