As as far as I have seen KERS has made less difference this year with fewer teams running it (but with all that has been going on there hasn't been so much analysis of when it has been being used). I get the impression that there is an optimal place to use it and most of the time that is where it is used, although I would love to see drivers try to surprise people using it elsewhere then try and defend later on (when the other car has KERS left) (any examples of this happening) I don't mind too much though because KERS isn't needed so much with everything else that is going on.
The tyres have been interesting, certainly better than the bridgestones - the most damning indication was Monaco last year, Alonso pits on lap 1 and stays out the rest of the race. Or at least it was stupid given that everyone had to use the hard tyres anyway. I would like it if the Pirelli hards lasted a bit longer to give more variable strategy - we saw how it almost worked out for Button today, and Hamilton/Alonso/Webber/Vettel may have chanced staying out after others pitted if only the hards were more durable. I don't really consider the passing moves due to extreme tyre differences as overtakes, much like you wouldn't consider passing a backmarker an overtake. It is just a result of different strategies playing out and unfortunately these are then considered as 'false overtakes'. (DOF_Power would be having a field day this year! I think we need him back to make everyone else see the bright side of things a bit more often
) There were however some great moves today, in particular the Button Massa Rosberg moves which left me speechless for a good while, you just ahve to look out for the good ones amongst the easy.
DRS has worked sometimes and not others - it has merely shifted the balance a little too far and now overtakes are a touch easy at times. I think it has been a little overused in the early races but they possibly wanted it to make an obvious change at first to avoid it being called useless (and some still did after Aus!). The best thing about DRS for me has been that it adds another layer of driver discrimination in qualifying, although I don't believe it should be free to use in the race. I also believe that if you had a sort of inverse DRS - increase downforce in the corners - the overtakes would look much better and use more skill, but unfortunately the risks of it failing are too great for this to be used.
All in all I think the regs changes haven't been bad but have just gone a little too far, but not by too much - we still have some great on track battles. I have still enjoyed racing this year although it seems there is little chance to stop and catch your breath - feel sorry for the commentators!
There is probably more I could have said about the rule changes but this is more than enough for now