It was definitely one of the best and most frustrating games of TF2 I've ever had. We stuck together through waves of robots, tried different tactics and ideas but we always got overrun by them, especially at final round.
The thing is, its actually a piece of cake in my opinion...when played on a full team of 6 players who know what they're doing. There were only 4 of us and despite we pretty balanced team there were too many of them.
When those two players arrived, it was really a godsend. Both identified themselfs as new to this gamemode (although the soldier one had a nice painted hat which is a sign of some experience, no offense to all free players out there), but they still turned out to be big help.
So next time when we'll play, I want a full 6 person team.
Also, for those who have no idea what are we gushing about, Team Fortress 2 has just had a new big update recently where they added a totally new co-op mode. In case you still havent played Team Fortress 2, go do it now! Its still free!
http://store.steampowered.com/app/440/