The effects look cartoonish, but it's not too bad. But I think those are placeholders. Overall it "feels" good - it's fun to play, looks nice, has very fluid gameplay and less 1 type of únit spam compared to normal aoe (Which is chariot archer spam 99% of the time). I'm sure I'll stick to it for quite a while, got me hooked. Which hasn't happened with RTS in a long time.
Also I like that most people play it on "fast" instead of "very fast", so it's a nice mixture of micro and macro. Plus it's less campy than AoE II, since you can't protect your villagers so easily. This makes the game more like Starcraft/Warcraft, which is pretty cool. Putting pressure on the enemy, re-establish the base, and loosing vills isn't so bad in AoE because you get more resources overall.
Stability is pretty excellent, much MUCH better than Steam AoE II, actually I didnt expect that, esp. since it's only a beta. Even with yellow connections.