Well I finally got to give mine a couple of runs on the weekend at my local track and I have to say I was super impressed
As I ran a 501x in 4wd last year I was able to directly compare them on the same track. I used my 501x shocks too so the cars set-up was as close as possible to my 501.
The car was far easier to drive than my 501x and seemed to have a little more on-power steering, but a little less turn-in (this was with the diff up front). It also jumped a lot better than the 501, both landing flatter and being more consistant.
For its first runs it was awesome
Next step is to try it with the over-drive front diff like the 501x and see how that goes.