I typically set up mail using mbox files in ~/Mail using procmail as the local MDA. Users then typically configure procmail to slice-n-dice their incoming mail into multiple mboxes under ~/Mail. This is a very standard configuration, but it's not one evolution supports. Evolution can be told to read one mbox under ~/Mail, but it can't be told to read a directory full of mboxes.
Yep, as painful as it is, you have to import each spool file by hand in evo 1.0.x. Already slated to be fixed in Evolution 1.1 (and might actually be in CVS... haven't had time to actually look recently), but that won't be shippable for Hampton.
Deferring until evolution 1.2 is out to verify it works there