I know this is an old thread but I finally got round to trying the new TB Isone and I much prefer the original Isone Pro. I played with TB Isone for days and no matter how I set it I could not get the uncolored sound I get with Isone Pro. To me the two programs sound very different. I am sticking with the original Isone Pro. It became obvious to me that even if I could get TB Isone to sound as neutral and uncolored as Isone Pro (I never could) it would not bring any improvement so it wasn't worth the effort. Isone Pro is still the most neutral crossfeed plugin I've used. There is some slight low frequency loss in Isone Pro that is not present in TB Isone but that is the only improvement and too many negatives.
I was able to match the two, but I can't remember the exact settings. If there aren't any features/improvements in TB Isone that's important to you, then you can certainly go on using Isone Pro. That's what I do, since there's really nothing in TB Isone I feel I need to have over Isone Pro.