casio has now posted the WK3200/3700 manuals on their japanese web site: http://ftp.casio.co.jp/pub/world_manual/emi/en/wk_3200_3700/wk_3200_3700_e.pdf

it looks to me like casio has kept most of the old sounds and added or replaced a few with "more advanced" tones. The acustic drum sounds have also been updated. As well as about 20 more arrangement patterns.

all in all i'm not sure if this is enough to get me to upgrade. guess i'll have to make a trip down to the local gear shop to find out. =)