So we're just about to roll out Exchange, and our schedule has
unfortunately been moved up by "pressures from above", so I haven't had
enough time to work out how I want to lay out storage groups, databases,
etc.

We have Exchange enterprise edition, with probably 300ish users, and I
anticipate 100 or gigs of data after the initial conversion. Multiple
storage groups seem like a good idea for backup/recovery purposes, but I
also would like to save some space on things with single instance storage
and such, which you lose with multiple storage groups if you're not careful.

How are other people laying out their Exchange data?