I have two machines - a Bernina 153 QE and a Janome Horizon 7700. Both are great, but each with its own strengths. The Bernina seems to do better at sewing over bulky seams without getting all those tiny stitches. The Janome is much, much better for FMQ - mainly because it has an 11" throat. Both machines are great and I do actually use them both a lot. I have a small Grace quilting frame and the Janome is far better for that. Also, the Janome feet are substantially cheaper than the Bernina, and it has a wonderful built-in walking foot (called Accufeed) which I love. The Bernina is smaller and easier to pack into a class. I wouldn't trade either one right now!!
I don't know anything about the Bernina 830, but I do know that Bernina is a good quality machine. I've had mine for 7 years and hope to have it for many more...