I spent pretty much the whole day playing the War Chiefs expansion pack for Age 3 today. As games get close to finishing up pretty much the whole company pitches in to beat on the game, find any last minute bugs and make sure we think it's up to our quality bar. I haven't played a solid day of any RTS in quite a while, and it was a lot of fun. Of course, it didn't hurt that I was on a winning streak...
We were all using max-level home cities, which is something I've never even come close to reaching in actual retail Age 3, so that was also an interesting twist for me. It is a bit daunting when you are just suddenly faced with a complete card set rather than incrementally building it up! Actually I find I really enjoy the HC leveling process in Age 3 so it was missing a bit of a spark to just start at max level.