Have you seen Thorzain vs DRG? The answer is 300 APM I guess :P
thorzain vs dongraegu g1 - YouTube

sc2 is barely a year old and I think the patches so far have been pretty reasonable. I think that a lot of 'imbalances' may disappear in the future when people figure more stuff out. I don't think one huge nerf will be the end to this.

What I can say from a noob perspective is that it always looked like Zerg was weak in direct engagements, but then Zerg can macro up so insanely fast, you get map control so easily with creep/mutas and you're the only race that can have a 300+ food army.