Underwhelming. Considering my flatmates decided to buy me SC2 since I was boycotting them (not sure how to feel about that, still), I might never get this.
However, I play with flatmates I have a platinum/diamond acct, so I know a bit about the mechanics.
Note: I thought SC2's unit mix was better than SC:BW but worse than WC3 and TFT.
SC2:HotS:
These changes seem good and bad.
I like the Shredder, it sounds strategically interesting.
I don't like the loss of the carrier. Protoss now have poor AtG, there'll be less need to check whether you need AA.
The replicant seems a bad idea, also. If you lack something, you should suffer - Jack-of-all-trades units reduce strategic depth.
HotS:Editor:
The editor was the most disappointing thing about SC2 (obviously apart from the new anti-consumer activision ethos).
I wonder if they will catch up on the things that TFT does better - such as pathable water (boats), high-resolution terrain (it's chunky at the mo), more cliff levels, and a far simpler/faster way to create custom units.
Anyway, the RTS crown seems ripe for the taking for any company ready to put a tonne of effort in, Blizzard is slipping.