i absolutely love my Janome 6600. i drool over the 7700 but given the difference in price have decided to stick with what i have.
if you can afford the 7700, give it a test drive. i would also recommend you check your Pfaff dealer if there's one within a reasonable distance. they have a model with all the same features but all the specialty feet snap on, which is much more convenient. in my area, both machines sell for the same price.
i love my janomes, but if i was ready to upgrade i'd test them both before deciding.