Got my Tank M1 w/ dumbbell holders. Easy assembly (thanks for the wrenches though needed my own for the db holders). Paper work and directions were well done. Only issue I had was with the front tire inflation adapter. Could not get air through it though it may have been me. Managed to find a filling station hose that allowed me to reach and inflate the front tire without removing the sled hood.
So far as performance, 4 workouts in I'm really impressed w/ the sled though, so far, I've only done basic pulling and pushing. Seems tremendously well made and durable with excellent attention to detail (handles, tires, powder coat, et al.) and the actual working mechanism appears to work smoothly and reliably while giving all of the resistance range I (and my clients) will need.
All said I'm very happy, after plenty of research, that I pulled the trigger and purchased the Tank. Looking forward to years of great workouts ahead.