I've got both the Callaham trem in a Jap strat and the Allparts one in a strat that BKP built for me. They're both very good, give more resonance and twang to the tone. When I went from the jap bridge to the callaham it was dramatic - almost as much of a tone change as pickups I have to say. The strat lacked body, twang, sustain and attack, now it has all 4......together with a good set of pickups it will make even an average strat sound top notch.
Downside, there's a very slight ring on the open G string, I've heard it in vintage strats too, I'm told it's down to the bridge design and is a trade-off for he great tone you get - it doesn't come through the amp though so nothing to really worry about!