I was given a modern (computerized) Bernina 820 and have found out quite a bit about them. The 830 is the same machine with an embroidery unit. The original owner was a previous Bernina fan but just didn't click with this machine. When she made the decision to return it, it was just long enough that the dealer only offered her less than half the value, which on an approximately $10k machine wasn't good enough. My friend offered to buy it (with the stand!) for half price and sewed on it for about 3-5 years.
Again, she didn't like it much even being another Bernina fan. She felt it was fussy with threads (recommends using Aurifil with the 820), and got herself a 770 with which she is ecstatic! She has a different brand of embroidery machines that has unique images she prefers even though they aren't Bernina. Going prices for the used 820s seems to be around 3k across the country, but she gave me the machine last time I came down to visit. Cost us about $200 to buy a box and ship it from Arizona to Seattle.
One thing to know about the 820/830, it has a proprietary sized bobbin that isn't L, M, or 15 and which means you can't buy prewound bobbin spools. We are all different and I became a fan of prewound spools with a long-arm machine because that machine couldn't wind a decent spool to save our lives! If I was doing embroidery, I'd personally want a big box of full prewound bobbins to just pop in and out. The bobbin winder is easy and fast with the 820, the bobbin is good, I'm just lazy and bobbins are expensive.
I used it hard for about a year, daily use doing piecing and quilting both and it did great. And then one night everything was fine, I turned off the machine and came back in the morning to finish putting on the last side of binding and it won't work. Or it will, about 1-2", 8-15 stitches (varies) and then a message light comes on. I can click the light and stitch another inch, everything is lovely stitch-wise, but then I get another failure. I'm pretty sure that it is going to cost me about $300 for a servicing and a thread removal, which is a price I'd normally look at buying a new machine at. But no new machines with that huge deep throat, the good lighting, the self threader, the BSR (bernina stich regulator) and built in walking foot.
Anyway, reviews and consumer reaction about the 820/830 was not good. Bernina did not admit a lemon but pulled it out of the line up very rapidly for a model number. It was a mistake to reuse the old model number (for those who say they love their Bernina 800 series, that's mostly the old solid workhorse and not the new model). I've sewn most of the last 30 years on a vintage machine older than I am after my then top-of-the-line (last one with cams, just before computerized) broke and was unrepairable. So I'm used to doing my own maintenance and tune ups, but I was determined to make the most of this fancy new machine and quickly grew to love the knee lift for foot up/down (my friend never used that feature), being able to tap on the foot pedal for needle up/down, or be able to use buttons. I have vision issues and have troubles reading the buttons but I've learned where the only one I really want is (cut thread).
Personally I think they had lemons/badly manufactured combined with badly designed machines and they had some that turned out ok or even great -- I'm putting mine in the ok category.
For under 3k and with a service contract or at least a one year warranty, I'd certainly consider it again. But I'd read easily found bad reviews first.