I am also a fan of the hard tracks (that's why I uploaded the old narrow version of The Island as an add-on), but I don't think 0.6 is better in terms of gameplay. In fact, I would argue that 0.6 feels quite a bit slower than 0.7 (assuming one plays on the highest difficulty settings). The fact that some tracks are getting a bit easier is not surprising to me as STK will cater to a broader audience, including children/adolescents. Also, the AI is quite a bit better now and we've just gotten an integrated add-on manager, so what's not to like?

I can certainly sympathize with the fact that going from 0.6 to 0.7 takes some time getting used to. As I regularly tested the development version while 0.7 was shaping up, I didn't get that much of a "culture shock", but some things did take some time getting used to nevertheless. For example, different driving physics meant that I tended to oversteer for a while, since I used the skid button more than necessary. But later on, when I very briefly tested 0.6 again, it felt neither as fast-paced nor as refined as now. There are of course still some issues with the 0.7 version, and I've not always liked the changes at first glance. Overall I feel STK 0.7 is a very different beast than 0.6, while keeping the basics similar, almost like the change when I went from TuxKart 0.4 to SuperTuxKart 0.3 back in the day.
TL;DR version: 0.7.x is the best.
