I use
the Line6 Toneport UX8, and it has a lot of things to recommend it, but it's definitely not as organic sounding as a good tube amp mic'd up in a good room.
That said, the good things about it for me are that it makes it very quick and easy to get a "demo-quality" idea down. Line6 has something called tone direct monitoring that in my experience actually works very well and makes the playing/recording experience very enjoyable from a latency perspective. I'm not sure how the Guitar Port would integrate into
mixcraft 5.0, but my UX8 is connected via USB to my Mac and the integration with Logic is smooth and sweet, and it never causes me to scratch my head and try to figure out why I'm not hearing what I think I should be, etc. That alone is HUGE for me, and again, it goes back to the fact that during the quick demo stage, it never gets in the way of the creative process. Also, speaking specifically about
the Pod Farm Platinum software that came with my UX8, if you can dream it, you can probably dial it up with the unbelievable combination of amps, effects, cabs, mics, etc, that are available as models. That can be very useful in the writing/arranging/demo process, and certainly provides a sonic palette that's difficult if not impossible to match with physical equipment for all but the most serious collectors with deep pockets. It's a very intuitive and easy to learn interface too.
Now for the bad...it doesn't sound as good as a real amp. Period. You can tweak the sounds to your heart's content, which is fun and cool, and you can get close, but it's not quite the same. In my experience, most of the models and built-in presets have way too much distortion and way too much treble in their default configurations, so you can improve things immediately by just dialing those down a bit. Also, playing with the tone and/or volume knobs on the guitar itself can help.
So, if you are looking for good demo quality, and you like to tweak (and have time to tweak) I'd say it's a good fit. Is it drastically better than Amplitube or Guitar Rig, etc? Not sure, but probably not. I can tell you that I briefly owned a StealthPedal and Amplitube, and the sounds were ok, but the integration into my system was not nearly as smooth and intuitive as it is with my UX8, and in the end it was frustrating enough that I got rid of it and switched back...YMMV. Also, I haven't tried
the Digidesign Eleven Rack but that is interesting with the way it supposedly reacts to the impedance changes coming from your guitar to the input. It could be worth checking out if you have that kind of budget.
You can hear the UX8 with Pod Farm in action on a couple of my tunes, specifically "Signs of Life" and "Falling Right In" (link below). I'm still learning to tweak, and not super thrilled about those tones, but it's an idea of what some of the relatively stock tones from the Pod Farm collection sound like.
Good luck with whatever you decide!
Best Regards,
Dave DeWhitt
www.soundclick.com/davedewhitt