I'm pleased with the overall balance of units. With proper scouting and foresight, any race can prepare and counter any attack. This game feels more hard-counter driven than some RTS games, especially StarCraft 1. I don't know if that means the game has been harder to balance. Because I play Zerg, I do feel like there are more limited starting options because of the Roach unit becoming such a staple.
The interface is a dream. I can do things I only complained about for ten years in StarCraft. Mixed building/unit control groups, tab-able sub-groups, visible attack queue-ing.... oh how much easier it is to control the game!
I'm going to start posting replays of interesting games here on the blog. I'll be using sc2rc.com to host them. Feel free to view them and post your thoughts here or on the sc2rc.com page.