I got a mail today inviting me to the pre-release version of Age of Empires Online, as reward for having participated in the beta. Release is on August 16. Age of Empires Online is a nice enough game, Free2Play, very accessible, with good-looking comic-style graphics, and I can only imagine it doing quite well. Personally I won't play all that much, but that is because I'm not a fan of real-time strategy games in general, and this shouldn't be counted against Age of Empires Online.
What I found interesting about Age of Empires Online is this trend which I would call the gamification of games. Age of Empires Online, like its offline predecessors, features real-time strategy battles on "instanced", not persistent maps. What is new in the online version is that there is now a persistent city you build up as well, complete with various building, resource gathering, a tech tree, and various quest givers. The quest givers are the link to the "classic" AoE RTS game, with each quest being a PvE or PvP RTS battle. Thus the RTS is the repeating core gameplay, and the persistent city is the game of advancement shell built around it.
There being a persistent part of the game allows Microsoft to sell you items in a shop like decorations for your city, which obviously wouldn't make sense otherwise in a RTS game. Who would bother to decorate his base on a RTS map, knowing that the map will disappear after the battle has ended? Your persistent city also permits the impression of permanent progress. A won battle no longer has zero effect on your future battles, because now you can use the rewards for winning a battle to craft gear for your troops, or advance in the tech tree.
This gamification of games, an outer shell which is persistent and works like a MMO game with permanent advancement and an inner core where gameplay is like it used to be, is quite popular these days. There are shooters, racing games, and pretty much every other sort of game you can imagine which now have an MMO-like outer shell part. If somebody were to make Super Mario or Pac-man these days, you'd see a persistent game of advancement between the levels of the game, with each level being a "quest".