So, now that Tidalis is out on Steam, some folks are of course wanting to register their previously-purchased copy of the game with Steam to get access to the Steam achievements and leaderboards (and organization in their Steam library of games, in some cases).
This is coming, but unfortunately it's not ready just yet -- I just found out this afternoon that it wouldn't be ready today, so sorry about that. There are some staff out of the office at the moment at Valve that are responsible for this sort of thing, so hence the delay at the moment. I can't make any promises on their behalf, but hopefully that functionality will be available soon.
Fair warning that in the case of AI War, there was a two week delay before we had that feature in place with them, but hopefully this time with Tidalis it will be a faster turnaround time. It just depends on schedules and such at Valve, I imagine.