I love all 3 of my Vikings. I don't have the 850 but someone posted yesterday on where she just bought it and loves it. She also has the Lily and it's a good machine too. If you look around, even on here you'll always find someone slamming a certain machine because unfortunetly they or someone they know had a bad experience. That doesn't mean they are all bad and some get slammed because someone is a die-hard Bernina fan or other machine and so therefore thinks all other machines aren't as good. I love my Vikings but know there are some other great machines out there including Janome. Good luck, have you test drove one at a LQS.

My Sapphire 830 is a great machine. No repairs and love the auto lift feature.
10 in throat area but do not like how low it is. Hard to thread and replace feet.
Never a tension problem. Drop in bobbin is a must for me.