These stages cannot be saved, which is a confusing design decision.
As far as single player features go, Brawl offers a lot to do.
Unfortunately, at the time of review, Nintendo seems to be having problems with "With Anyone" matches, although connections through Friend Codes work.
There is a 64-friend code limit, so choose your friends wisely.
The general multiplayer is available for online play but exclude the co-op Subspace Emissary adventure mode.
With strangers, you will be limited to two-minute free-for-alls or team battles.
That, however, is not enough; the heavily touted Subspace Emissary is not as great as it may seem.