I have been using amp sims through my computer for a while. I've learned 2 important things about amp sim plugins I've tried: spring reverb and tremolo aren't really accurate or musical. Since I cut my teeth on a mid-60's valve amp that had both an excellent spring and trem, I've noticed something missing in sims, no matter how good the amp/cab model is. It doesn't sound 'right' to me without a proper spring tank and tremolo. The question I asked myself was whether this tremolo would be able to match hardware for musicality. The Tremolator goes beyond, into depths I don't really need to delve, at least for a nice tremolo on a Fender-ish amp sim. I am not so sure a hardware trem will beat it, even at basic settings.
I got it on sale, so it was absolutely worth it, to me.
As for the Spring Reverb, I bought a real one (cough Surybear cough). ;-)