I still don't have Xperia (should arrive today) and after them I'll try iGo.
It works exactly like TomTom, no online connection is needed.
In terms of interface and fexibility (options) iGo should be better than TomTom, but there were complaints about routing quality, so I'm not sure.
It has TMC but I doubt that it would work on X1 without additional hardware (special TMC receiver).
Actually, TT7 works on Xperia as well... but that can't be discussed here.... ;)