I am by no means an expert, and I can't play online much (haven't for quite some time now) due to work and family but I do practice versus the AI often for the rare opportunity to play online and at least be somewhat competitive. With that being said, the answer to your question is yes. Hot keys are still important. It feels like a lot more point and click than AoM, but hot keys are important, none the less.
I believe that practice is a good idea, especially since I can't play online often. This is what I do: Practice advancement times versus the AI especially if you primarily play 1v1 online. Figure out the right combinations of villagers to maximize your advancement while still maintaining a comfortable economy. That may be the single most important thing. Always watch your villager numbers. More is better, but I'm sure you know that. Still, always watch it. Once you have that figured out practice your micro and countering skills while still advancing ages within the time frames for your civilization(s) and strategies and getting the most villagers for what you're doing. Practicing economy balance will be derivative of these two things as you continue to practice. These things have helped me while playing random games versus average players.
You're absolutely right that the AI is no substitue for a human opponent, but practicing these things will help to prepare you for the average player online and give you an advantage on them. The best thing in the world is (when you get online) to play against folks who are better than you, when you can find a willing player. Many are very gracious after the game in helping you to identify flaws in how you play, at least they have been to me. When I play online, that's what I try to do.
Good luck and maybe I'll have time in the summer to meet you online sometime.
Inigo Montoya: "You seem a decent fellow. I hate to kill you." Dread Pirate Roberts: "You seem a decent fellow. I hate to die."Still playing the best RTS ever, Diplomacy. It's called a "board game." You must actually interact with your opponent...such a novel concept.