i have a viking 350, about 14 years old. I love this machine....but, right now i have a bernina 450 on layaway. it was a classroom machine at my LQS and so am getting it at a reasonable price. I'm still paying it off, so i will let you know in a few months how i like it (when it arrives here!). At this point in my life (Katie a senior in high school and going away to college, nate in fourth grade), I cannot justify a $5K or more machine. I'm very happy that my husband supports the idea of the bernina!
My advice to you would be to go to different dealers and try the machines you think you are interested in. bring your own fabric...for example, if all you do is quilt-bring fabric and some small quilt sandwhiches. if you also sew clothing (like i am attempting to do), bring examples of the type of fabric that you sew with. and test on your fabric samples. heck, i even labelled them so i could then line them all up and compare. Bernina won hands down for me.