I got this accessory kit from my dealer last Friday. This is not the tension upgrade with replacement parts I was talking about in the first paragraph of my reply. This kit really deals with problems with specialty threads and additionally gives us a new nifty oiler and tool to get out threads stuck in the bobbin area.
Yesterday I did a comparison test bwteen this kit and the Wonder Thread Guide. They both work, at least for me. However the foam rotary disk doesn't allow large thread spools (including Superior 1000 yd spools) to spin freely. So you have to put them on the supplemental spool holder. The thread still comes off the spool overhead but the thread now travels through 2 additional "eyelets" before entering the 830. This appears to get the kinks out. I sewed out the same design on the same fabric, stabilizer, speed, tension, and with the new needle using my most troublesome metallic thread. I used the lubricator with the Bernina setup but not the WTG. With the Bernina setup, the thread broke twice which was a VAST improvement. The WTG did not break. I have both setups on my 830 standard spool holder now, so I guess it depends on which works the best for the particular project.
My dealer is still taking my 830 with him to Steckborn next month. The tension on my machine is still wacky since I have to tighten the bobbin tension significantly and loosen the top tension to get a good stitch and good embroidery. In general, I love my 830 but there are still times I have to give it a little verbal encouragement to get it to behave properly!
Looking out the window at Lake Leman in beautiful Switzerland