6D - new cool features
Whilst the GPS feature doesn't seem so sexy (some will love it!), the Wifi option is great news.
Whilst many are focusing on AF (sorry), the wifi option will actually allow a new way (well, more affordable than previous options) of wireless 'tethered' shooting that will be so cool for many (staying in your car during those cold night shootings, yeah!).
Easy control from an Android phone or iPhone as well as tablets and PCs will enable some cool stuff, and means this feature will soon be integrated in more DSLRs, yeah!