I have used Amplitube 2. It is fairly good for an amp sim, but for the money that you pay for it it could be a little better. Guitar rig 3 sounds better by itself, but the tone is too fat so it doesn't mix very well, I think AT2 might mix better. It's got a bunch of different amp simulations from different eras and you can even change the tubes in each and the cabs that they go through. It lets you choose from a few different mic simulations and even mic position and distance (only a few different settings, as opposed to a lot of tweakable settings). Also has a bunch of vintage FX pedals with fully tweakable settings. I've found a couple of really good sounds in my experiments with the program, but it's a RAM hog. Jeez, now that I am saying all this it's making me want to go back and play with it lol.

I'd say go for it, you've got nothing to lose.

Check this one out. I haven't forked over the cash yet, but the demo online is really interesting - especially the feedback sim.

http://www.softube.com/

jg49 wrote: I was thinking of adding guitar modeling software to my bag o' tricks mostly for scratch track reording when drum tracking as I don't really have good room for isolating a guitar amp.

Edit: Forgot to add the link cord blood banks

i have it and for that purpose its perfect. what i find easy about it being a "fender" plug in is that pulling up sounds is relatively quick and easy as the names are all the same as the fender amps you know (i have to admit i have a hard time figuring outall the nicknames that plug in manufacturuers give to the hardware they're emulating). plus you get to "record" with amps that normally have to be really loud to record with in the real world.

in my opinion the best amp of the fender plug is the bassman. to my ears (and with my strat and my vintech x73 ) it sounds like the real thing!

S4G "(i have to admit i have a hard time figuring outall the nicknames that plug in manufacturuers give to the hardware they're emulating)."
Amen to that, I have a Korg multi effects pedal I use live sometimes and it took me forever to figure out their lawyer required doublespeak as to WTF the samples were. This is fine when you have the time to tweak it the way you want and save it but for a visiting artist I think it would be very perplexing. I could use the pedal for this, it does have Fender, Marshall and Vox amp models but the way the controls are laid out and the fact that is a floor pedal it is definitely not intuitive.
Most of the artists I record are folk/rock/blues orientated and many already use Fender products and the fact that the GUI look like amps I hope will make it easier for them to dial in some sort of sound on their own.
I looked at the softtube it is pretty pricey, if I was going to use it on a regular basis it isn't that bad but I am uncertain if I would use it outside scratch tracking. I know these emulations have come a long way but is it really going to replace amp/mic in my normal recording?
My other concern is latency, my computer is at the high end of the recommended specs but tracking 8 or 16 tracks and adding this has me concerned.