Comment from GPG here: http://forums.gaspowered.com/viewtopic.php?t=36103
Originally wanted to have a replay manager in-game for the first patch, but networking updates took most of those engineering cycles. Replays work, but a few annoying bugs like lack of sound make them unshipworthy. Expect this in one of the future patches after internet play settles down. Brad is a big proponent of them, we just want them relatively bug free.