ive been using ssd's for about 5yrs i think, and it's well worth it.
i now have 2 of them, and they are getting cheaper (relatively)
just put the OS there, and some of your favorite games or if you have some apps that needs the boost. just remember the space limitation.
my old ssd, an intel, boots like 13sec (after the beep). you don't need to buy the fastest out there, any decent ssd is a lot faster than mech drives. my old intel is even sata2 (new one is sata3).
a good choice would be samsung evo, or crucial mx100 (not sure of the model). get at least a 120gb, 240 if possible