Just giving 2.1.0-beta1 a whirl. I tried to import from a previous copy, but got an error message. It seems if you have a prefix on your DEF file names it will fail. IE: This error occurs,

Import error: CRITICAL ERROR OCCURED: Cannot open /collinscom/admin/defs/category.def:

but my DEF files are called foo_Category.def , etc. There seems to be no way on import to specify a prefix.

Oh by the way.. the word Occurred is spelled wrong in the error message.