I have one! I bought it about six months ago and I LOVE it. I have the J table and my Janome 6600 fits perfectly.
It happens to be nearly identical to the table my grandmother's industrial Singer is installed in, a table that is probably from the 60's. Except hers is a funky green.
This table is a serious piece of furniture. Solid as a rock. I am not a light person and I have stood on this table and it doesn't move a bit. If I ever move I will disassemble it first because it is HEAVY!!
Assembles very easily, I put it together in just a few minutes. The height of the shelf that the machine fits on is infinitely adjustable via very long screws so I was able to precisely line up my machine bed with the table top. The top itself is also adjustable but not infinitely adjustable; there are several different heights it can be set to. I was able to set it to exactly the height I wanted so I got lucky there.
Not cheap and not portable, but it's extremely sturdy and that's just what I was looking for. I was tired of the "bounce" from the table I was using at the time (long Ikea table). Shipping was fast, it came with easy-to-read assembly instructions, and nothing was missing.
Only thing I can think of as a drawback is if your machine had a free arm I don't know how you'd ever use that part of the machine with this table. But the Janome 6600 doesn't have a free arm so that's not a worry for me.