I know Lin and Mac users can easily compile engine themselves, but in case a linux user wants to play with windows user, who cant download and build from hg there may be problems with sync.
I mean: There are changes to source during day, so if I want to play quite up-to-date version with someone using Windows I have to download and build soon after the nightly build, as later there will be changes and compatibility issues. And I have to repeat it each time my friend downloads new nightly build... Quite a pain.
Also there are linux users, who cant compile themselves, and these are happening more and more often(its fault of Ubuntu and other user-friendly distros). Same for Mac OS X probably.
So my idea is to put there Windows, Linux and Mac OS X binary packages along with all-in-one one in case somebody wants portability.
And as for portability there should be option to make OC save configuration files to its own directory in case somebody wants to play it from USB stick. Maybe even add "portable binary package" with this option automatically set to yes.
Also some archiving would be good. I think there should be some insight in development of OC with 'backups' for every day in last week, every week in past 3 months, every month in past year and every year. Maybe also for each milestone. But thats just idea.