I've had my new-to-me Bernina 820 for a bit over a year and it's hard for me to answer that question. I had the option to learn its features and use them, or just keep pretending it didn't do anything more than my previous vintage machine. I know what I use and like and have already. So... my Bernina has the integrated walking foot and the BSR, I've used both as well as tried out the regular stitch for quilting down. Like them all. I'm mostly going to be using the serpentine stitch and the BSR for quilting. My friend suggested that I just keep it in walking foot mode while piecing since all I do is quilt, it is easy to take in and out, but mostly I just keep on my quilting foot and let it walk... It is well lit, easy to thread, and has a huge throat.
Although I've had my machine on the table top for decades, I'm really wanting this to be sunk down table level for quilting, even with the extra wide bed. It's not that it is flimsy -- but it feels like it to me and it is awkward. My goal for this year is to find an affordable sewing table that will fit that machine. I will probably still rise it up to piece with, but lower to table top when I am actually quilting.
My machine does not do embroidery so have no opinions on thread holders in that way. Typically I just use one thread at a time and it isn't an issue for me. However, my machine is in the shop now due to an error screen that shows the problem as the thread entering my machine -- it's either a thread sensor malfunction or it just needed cleaning, in any event, I couldn't clear it myself. This model did not go over well with the public and seemed to have a lot of mechanical/computer errors especially related to threading.
My main negative with the machine is rather silly, it has proprietary bobbins which are not cheap. They are extra large and are not a standard size, you cannot buy prewound bobbins which I've grown to like. It's easy to wind the bobbins, but I'd prefer to have a big stack of bobbins ready to use. If I were to buy anything, it would probably be more bobbins.
For features I like, I just did a set-in square version of Lemoyne Star on my back up portable class machine and really missed my thread cutter. I hear complaints from others that their machines leave long tails -- not the Bernina, or cut too short and they lose stitches, again, no problems there I find them just right!
I love the knee lever for foot up/down. My friend who gave me the machine never used it. My model allows me to set the needle up or down with a foot tap - this is the greatest thing since sliced bread! Yes, there are buttons but I have vision issues so I can't read them and don't know them well and when I'm guiding my last bits of fabric I don't want to be taking my hand off and pressing a button. I have learned the location of that cut thread option, and by then my hand is coming up and right past the button anyway.
The self threader is nice and one of the reasons my friend gave me the machine. Again, with my vision issues some things are just getting harder and harder. Threaders can get out of place on any machine but I'm finding it works well and consistently. My cheapo Brother I'm using has a better threader assist than any of my vintage machines, for them I use one of those hummingbird shaped needle threaders.
Again, I don't have the embroidery module but I did use the built in stitches to repeat my hubby's name along the bottom of his bowling towel... (it's to wipe the ball). The fancy stitches will be used less than 1% of the time for me, so far as I can tell the accessory pack that came with the machine will have everything I need.