This was a great ~3 hour one-shot (we just played the basement level). The pregens are hilariously zany, and the premise and setup are fabulous. It's worth investing a few extra minutes in the prologue, hamming up Tunnelmaster Miknik and the cheering/anxious Hookclaw clan, to set the tone.
The encounters were fun to play, had a good variety of challenges/abilities, and were surprisingly tough for a light-hearted one-shot. But IMHO at least one of the basement encounters needed some kind of social element, rather than "you enter the next area, X creature attacks [two of whom can't even speak]". In hindsight I'd have given Camilla some sort of charm/suggestion spell and lead with that before things turn to violence - that could make for some great (but also poignant) fun.
As it is, the adventure really needs the players to embrace the spirit of the adventure and their chaotic/crazy characters. If they do that, you'll have one of the most fun 3-4 hours of your recent roleplaying lives. If not, it's still a good fun one-shot, with a fun twist on the classic 5 room dungeon. 4.5 stars.
Note that there is a very high quality, free fan-made VTT map available too.