Well, I had the very same question. When the II was announced in 2011, we were in a bit of a financial bind paying on 2 mortgages. We had moved into our new house and were prepping our old one for sale. So, springing for a new AxeFX wasn't on the table, especially since I was fine with my Ultra.
Fast forward two years. I'm still very happy with my Ultra, but I took the plunge and bought a II. To be honest, I had not heard any sound clips on the Internet where I felt the II totally blew away the Gen 1 AxeFX. However, features such as USB, headphone output, tone matching and Scenes seemed enough that I was willing to try a II out.
I have to say that after the first couple of chords I strummed on the II, I knew that it was a completely different animal. More tonal complexity in general. Definitely something more there as far as amp modeling. It's really something that you notice most when you're actually playing in the room with an AxeFX 2. Don't go strictly by sound clips on the Internet, when you're in the room with an AxeFX 2 the added "organicness" of the models really is noticeable.
I love Fender cleans and while the AxeFX Ultra did a good job, it wasn't quite "there", but it was "close enough". I did an A/B with my Blues Jr. and the AxeFX II's model, and the AxeFX II was pretty much dead on.
Another thing I noticed was the much improved workflow. Things like the quick control knobs are a huge productivity boost. And little things, like the improved tactile response of the front panel buttons and the snappiness of the front panel screens were noticeable.
The first 80 or so presents are simply the amp, a well-paired cab and a bit of reverb. That's it. That's such a smart way to organize presets. You can get a feel for the amp models in a clean, uncluttered by effects, setting. That really gives you a chance to get in, tweak a particular model the way you want and make it your own.
So, I'm still in my honeymoon phase, but so far color me highly impressed. The Axe II has exceeded my expectations in every way and I wish I'd made the jump earlier.
I figure with the sale of my Ultra, which should net $1200-1500, the Axe II is a bargain.
I want to do a comprehensive review, but honestly I'm spending too much time playing and enjoying my Axe II. I'd say do it. You have a return period, so nothing to lose by trying it out!