Wow...sorry gents, I had no idea this thread had taken off this much, I don't come here that often. I chucked the weekend at it, upgraded to quantum and bought cab pack 13, and I'm pleased to say that clean and crunch tones sound much better to my ears. Perhaps still not AS good as they do with a real cab, but definitely improved (I should note, I upgraded from FW15 - I stopped upgrading because I could barely hear a difference between firmwares and I got tired of the endless hype surrounding new ones. It seems the bigger jump emphasised the improvements). So yea, pretty great on that front.
That said, I cannot for the life of me get a good modern, high gain tone going. With my cab, it's a simple matter of calling up a modern sounding high gain amp (5150, one of the FAS moderns, etc.) and you're there. I've spent all weekend messing around with hundreds of IR's, mixing them in cab lab, (you know how it goes) and they still all just sound...bad to my ears. Kind of harsh, gritty (not in a good way), boomy, one dimensional, and lacking any sort of oomph. Truth be told, I'm getting pretty frustrated now. As ever, I'm not bashing the axe, it's a fantastic unit and I'm almost certain it's my problem because everyone else seems to get amazing tones out of theirs, but it confuses me a great deal that you can plug into some of these amps in real life and get a great tone off the bat, and yet with the axe it takes me a great deal of tweaking to get a fairly mediocre one.
Rggggh.