I just added an SSD to my system a couple weeks ago, an Intel 330, which is not as fast as the Intel 550 line, but still a decent SATA 3 hard drive.
I have to say that i haven't been totally blown away by the performance (though maybe that says more about my expectations than about the HDD itself). Boot times are quicker for sure, just over 20 seconds from power-on until i can start opening programs. Programs are snappier too. But the difference over the conventional drive i was using seems more quantitative than qualititative.
One thing to add; at first i thought i had the SSD properly hooked up to a SATA 3 connector...then i figured out that i in fact used a SATA 2 connector -- hooking the drive up to the proper connector definitely made a pretty big difference.
Regards
Glenn