I'm very excited for Heart of the Swarm. I really liked the story in Wings of Liberty (don't think it was nearly as good as the story in the original StarCraft + Brood War, but I digress) and I'm excited to see it continue.
What I am most excited about for what it adds to multiplayer aren't the new units (I play Zerg and it seems like they're just adding back in abilities from units they removed that used to be in the original StarCraft), but some of the new features. The ability to watch the same replay with others is exciting, as is the ability to actually launch into that replay at any point and "rewrite history" by playing the game from that point. My brother and I will be utilizing that to maximize our strategies as we tweak them and see what works and what doesn't. Heck, if I'm out of time and want to pick up a game on some other day, we can just quit and resume from the end of the replay later (assuming a match between my brother or some friends) It's also great that you can use that same feature to reload and continue from a game if your connection was dropped or something.
I'm also excited that they are bringing "back" Global Play. I met my best friend through StarCraft back in 1998. He lives in Sweden. We've only each been able to visit the other once in person so, needless to say, we haven't been able to play StarCraft II together. FINALLY Blizzard has realized the error of its ways and is about to unlock the regional restrictions, finally! It doesn't bother me that stats are tracked separately in each region - I can work with that.
I remember playing SimCity when I was much younger... I might give the new version a shot. It looks like it could be good