I think you'll find that a very large percentage of folks that have the 6600 love them, myself included.
But ... what model is your Bernina and what features does it lack that the 6600 has? If those features are very important to you then by all means trade (or as others mention keep the Bernina and buy the 6600 - even if you buy a nice used 6600 from a reputable dealer).
The features of the 6600 that I simply will not do without: Integrated dual feed foot (including a foot with 1/4 guide - I piece with a dual feed foot ALL THE TIME), needle down on stop, thread cutter, and wider harp than a lot of machines. Others have also said they love the separate motor for the bobbin winder so you can wind a bobbin while sewing. The one time I tried to wind a bobbin while I still had my top stitch thread threaded through the machine - the two of them got horribly intertwined and created a great big mess (and I wasn't even running the machine). I think that was a "user" problem though as I seem to be the only complainer in that camp
