Built a tour rack for an art installation in the 5U multiflex rack from Thomann, it's pretty nice, got a fair few gripes though that are specific to my use case.
I had to add rear rails myself because the Thomann site didn't include an option to buy them seperately in the correct length (as far as I could find). I'm not a huge fan of the extrusion style rack strips with loose nuts that come with the case, would much rather normal rack strips and cage nuts (I guess I'm a glutton for punishment). Also, having a little more depth between the front rails and the lid would be nice for connectors (maybe have a few sets of holes and screw in the rails so you can customise the depth to your needs), I can imagine if you have a piece of equipment with long knobs or want to have connectors left patched in it could stop you from lidding the front of the case (my rack has a network switch in the front with some cat6 cables that are quite squashed when the front lid goes on).
Construction wise, it seems pretty solid, I wouldn't go dropping it off the back of a truck any time soon but for touring with people that know how to take care of equipment it should last a fairly long time. The lids are a nice way of adding a bit of protection to the rack without needing a full flight case. They fit well and being able to stand the rack on its back is quite useful.
Weight isn't horrendous, once you've filled it with equipment it won't make much difference. I'm able to move my rack around on my own without issue, having the slots in the side to handle from make it a bit easier to manouver around as well.
Overall, a pretty good rack but it could be made great with a few small tweaks.