digital modeling effects

[Bill Rickles]

I see a lot of mention of effects units on the forum, such as Profex. I assume these units provide reverb,sustain or whatever.
Is anyone using the Modeling effects units such as the Digitech RP2000. According to the literature these units will give you the warm tube amp sounds or any combination imaginable along with reverb, vibrato, rotating speaker,etc. Yamaha also makes modeling amps with the same claims. Any comments?