At the moment, I find the TC4 to be a real challenge. I'm running foam on carpet, though, so maybe people running rubber tire outdoors are having better experiences - I can only hope.
On the drawing board, it does look like a "better" (and I use that term loosely) design, but I'm having a very difficult time getting the car to run fast out of the corners. It has this nasty on-power push that I can't get rid of. I have such an absurd setup on the car just to get it in the ballpark, and there's still a long way to go. Experimenting with everything from roll centers to swaybars to swapping the toe-blocks all around from front to rear and back again to try and find the magical combination - the normal logic I got accustomed to with the TC3 doesn't seem to apply with this chassis.
Of course, I think back and I'm sure it took weeks to get really comfortable with the TC3... and I'm only at 6 weeks with the TC4 now, 3 of which with full option parts available.