I noodled around with one at the store and wasn't impressed. For strictly recording it would be OK if you just need something to get lots of different amp sounds that are about 80% OK but probably sound fine on tape.
I hated the way it "felt" ie. it had the typical solid state feel and I wasn't really wild about any of the preset sounds. The effects seemed to be way over the top but that could have been something else in the rack that I wasn't aware of. I think there was an Alesis delay unit that was throwing something into the mix. I was playing this thing into a Mixer and a set of PA speakers via the onboard emulator.
Back to the feel...
I have a rack mounted Tube preamp/poweramp rig and it plays like a regular amp. I really don't like the feel of the amp modelers I've tried. They lack something (Soul I think...) and the sound isn't quite right. I'd rather buy a nice head like the new Genz Benz Diablo or a Mesa Boogie and learn to dial it in. I have an effects processor that I don't use much of. Just a bit of delay or reverb here and there, maybe some chorus or a flanger sometimes.
I think the thing would be impossible to use effectively live, but that's just me. If you want to go the modeling route, stick to the line6 stuff, they do it best. Or buy a nice head and run an effects processor in the loop.