It's quite instructive to talk to big (>10000 employees) companies who tried to migrate to Google Mail/Apps. There are nice disaster stories around.
The inbox size vastly increased (500MB => 30GB) which makes the record keeping much easier, just never delete anything. Before we had to empty our mail into offline archives.
Everyone still uses office for word processing and spreadsheets. The online storage is nice for sharing files though.
We do pretty well with a more or less entirely Google Apps workflow.