First, for anyone in the US nervous about ordering from Thomann, I've had two great experiences so far, this stand and its accessories being the second. I chose the cheaper UPS shipping option, vs. DHL, and it arrived in the timeframe of the more expensive option anyway, even with Christmas during the shipping time. UPS clearly made some effort to destroy things, but the stand did arrive intact.
This stand is shockingly lightweight, but shockingly sturdy given its weight. I was initially nervous about putting my OB-X8 on a single bar, worried it would tip off, but once I tightened things down and inserted and tightened the additional rotation locks for the tier, I had no worries.
If you are solely using keyboards, I am skeptical that more than four tiers on this stand is really practical. You very quickly lose sight lines to controls on the upper parts of control panels and/or have keyboards at poor playing heights using more than four tiers.
What I did was use the lowest tier all the way at the bottom of the stand to hold some pedals and keep them off the floor. You can also repurpose tiers to the back for some creative uses, mine being to hold a stage box almost vertically, into which all the keyboards are plugged. It also may be more economical to buy a stand with extra tiers than it is to buy a strengthening bar and extra arms. Note that tiers cannot be removed without disassembling the whole stand, though arms can be removed without disassembly.
I'll note that the "narrow" 6D-105B is still pretty imposing in a room. It was wide enough to handle the OB-X8, which was the widest keyboard I planned to house on this stand. I cheated beyond the base 105B width with some of the Jaspers monitor arms to hold a few knob-controller devices.
Overall, I am -very- happy I spent the extra money and shipping cost to get this vs. the On-Stage 7903. Reviews for that are rife with tales of falling keyboards and the accessory selection is not even close to what Jaspers offers.
Yes, this was pricey, but I now have an eminently useful and reconfigurable setup that should last for decades.