I think Revalver 4 is a pretty useful tool. The amp modeling is decent to good depending on the model but I think the ACT module is the thing I keep coming back to.
It has a tab that takes a snapshot of your guitar and creates a profile, then you can apply different instrument simulations to it, like acoustics (nylon string, steel string, resonator), vintage guitars (Les Pauls, Strats, Teles) and weird guitars (Dan Armstrong). The acoustic simulations wouldnt fool me if they were mixed forward in a sparse arrangement but I really like them for blending in color tracks in the background or enhancing clean parts. The classic guitar emulations are cool for changing something subtle on one side of a distorted guitar mix without having to actually change guitars and deal with the differences in intonation between instruments. Supposedly they are actually creating an amp profiling module that is not just a match eq based thing (unlike BIAS) but it was sort of announced months ago and still hasnt materialized so it could just be vaporware at this point.
I like Recabinet 4 the best in terms of tone and sounding closest to a real amp. I like X50 for quick good sounding results, my only gripe is that its kind of limited in what it does. Also IK is releasing Amplitube 4 soon which is on discounted pre-sale now. They have supposedly done something different in regards to cabinet simulation that is a combination of IR and algorithm, but at this point its just marketing speak and may not be anything noteworthy. The IK Neve and API emulations as well as the Mesa pack have me thinking that they could be the one to beat real soon.
