New versions of BIAB are always worth the money. There may be no one particular feature in the 2005 version that stands out for you. Keep looking. There are a great many features and a nice collections of bundled add-ins.
Check out the discussion on BiaB's user group to see how the new version looks to BIAB users.
http://www.pgmusic.com http://www.pgmusic.com/cgi-bin/Ubb/ultimatebb.cgi?ubb=get_topic&f=1&t=005630 .