The main issue you will face in online play is quitters and desync issues.
You'll have to get used to not finishing games. In the usual 6 player quick FFA with strangers don't expect to be able to finish your game. Once enough players drop the game becomes very stale and pointless. If you adopt a different attitude and treat every game as practice and refinement it can be a very enjoyable experience. Just don't get attached to the idea of playing every game to the end.
2v2 matches, on the other hand, are much more reliable and you can expect to play them through most of the time. 2v2 is very enjoyable and challenging.
Multiplayer can be frustrating at first, but ultimately I find playing against humans much more fun and rewarding than playing against the AI, and that goes for most video games in my opinion. Freezes and crashes do happen but you just have to live with it until they get patched. The AI is dumb as usual, often an opponent will quit after you've been in trench warfare for 50 turns and the next turn the AI will move all those units out of their forts into a killing zone, that sort of thing.