http://technet.microsoft.com/en-us/library/ms188388.aspx

I agree - do one at a time, and just let it run to completion, however long it takes - if you do an OFFLINE rebuild, it's faster, but it is indeed offline for the duration. Make sure you've got plenty of tempdb space if you're using SORT_IN_TEMPDB = ON, and plenty of free space in the database.

I would absolutely REBUILD them if you can afford to - you get better ending results. If you don't have Enterprise edition, and can't afford the downtime of an offline rebuild, then you may be stuck with REORGANIZE, though, since you need an online operation to guarantee users won't be stuck.

See the

ONLINE= (ON | OFF)

syntax.

Note that ONLINE = ON is only available on Enterprise edition.