when i switched from my old crt (72 hz) to my lcd (60) i did notice the change at first, but after a few days i really don't notice anymore. thus i suspect as long as it doesnt bother your eyes after a few days acclimitization its no big deal either way.
junkie, what lcd do you have that can manage 75 hz? also whats its max resolution?
also, dunno if this is just my own system's quirk, but i notice the hz difference alot less when i've got the lcd plugged in via dvi at both ends. the adapter seemed to mess with things *shrugs*