tremel-no is great! even if you use your whammy bar all the time, simply from the point of view of locking it to change strings, it's great! and once you're used to it, it's quick and easy to lock and unlock it.
i don't think it really changes the tone much, although i'm sure eric johnson would disagree (the ones with the black screws sound better...) but i think it does change the attack, simply because there isn't that slight movement from the bridge when you hit the strings.
there are also hardtail conversion bridges out there, if you wanted to convert a trem strat. and of course, warmoth et al do non trem strat bodies.