I did a test import on 1.2 Beta 4 and it took (28 hours 4 minutes 34.21 seconds) to import just the posts alone . I should note that I did the import from a backup database while my live board was running so I'm sure that slowed things down.
I started the import before beta 5 came out so I'm wondering if the new and improved importer would have any effect on the amount of time. Anyone know about that? Maybe @Brogan ?