Eurogamer weighed in (7/10):
http://www.eurogamer.net/articles/2011-08-17-age-of-empires-online-review?page=2You can certainly play Age of Empires Online without handing over any money, but the very best free-to-play games value their non-paying communities because their sheer mass and commitment support the top five per cent who pay for the thing. Age of Empires Online does not. In the long term, it's crippled for free players: no ranked player-versus-player, certain units unavailable, a stunted tech tree, limited crafting and limited storage. If you have no plans to spend money, look elsewhere, because AOE Online does not do the business model justice.
In fact, for paying players, it's even worse: £15 [almost U.S. $22] for each civilization (at the moment, Greek and Egyptian; the Greeks come in the £20 [almost $29] boxed version) or a whopping £80 [$115] for the season pass, which grants you all content released in a six-month period. If you want the new civilizations down the line, cough up. To play this game long-term will cost much, much more than its competition.
...
It breaks my heart to give Age of Empires Online a less than brilliant score. If you'd told my teenage self that, one day, AOE would have this much content and you could play it online against actual people for free, my spotty head would have exploded. It's as good as mechanically identical to previous entries in the series, and although its new structure spreads it a little thin, there's still a fine strategy game underneath it all. But the context has changed.
Age of Empires, great as it was, doesn't quite stand up against the best in the RTS genre today - and Age of Empires Online doesn't improve on its mighty predecessors in any meaningful way in-game, while adding a lot of bumf around it of questionable value. It's still a grand name, of course, and in some ways a grand game - one trumpeted as 'Microsoft's triumphant return to the RTS genre!' So let's put it this way: it's certainly a return.
It seems, like Relic and it's now deceased Company of Heroes Online, RTS makers are struggling to develop some sort of F2P MMO-ish format that can pull in some steady nickel-and-dime Internet-store revenue since most RTS-devs can't pile up the number of sales Starcraft does, and C&C and AoE franchises did in their heydays. Blizzard notwithstanding, the days of the RTS gravy train seem to be over.
*The fact it requires Games for Windows Live (I thought that was dead!

) will probably scare quite a few folks off, fairly or not.
Three words: League.. of.. Legends.
Riot Games has finally unlocked the recipe for the succesful, lucrative free-to-play MOBA-style game. RTS developers needs to follow their example, because, yes, no RTS will ever be succesful as 'Starcraft'. The genre doesn't have that big of a mass appeal. But it is possible to create a succesful MMO RTS if you play your cards right. Unfortunately, it doesn't seem that Microsoft played their cards right with 'Age Of Empires Online'. 15 dollars per civilization? Oh, come on!
Why not make it 5 bucks per civilization? Then charge little bit of extra money for civilization 'wonders'? That's how they could make their money! Riot Games' LoL charges 5 bucks per new champion and about the same for new skins for those champions... and the results: 15 million signed subscribers and explosive game and company growth.
Trion's upcoming 'End Of Nations', which is looking attractive, just announced that it'll be F2P. That's a step in the right direction for that game's hopes.