All in all, I must say they're pretty cool. Not a must-have, but better than the Crumb gang.
Bubo's very large. I'll get size comparison soon. The other critters are also larger than the creatures with Crumb, so the $40 feels better spent. Also, Bubo feels to be quite solid although he is hollow.
Bubo's strap and real chain is nice, although the weight of the chain tends to pull the strap over. Also, the strap itself is a bit large for Bubo -- it could have been a tighter fit around the shoulders. But the paint job on Bubo is excellent, and the sculpting detail on par with Jabba.
The rock wart and womp rats are also highly detailed. That rock wart is creepy as hell, whatever it is. Nasty. The rats are funny -- one screaming while the exclusive scratches itself. In this case, the exclusive is well worth it because it has so much personality in the moment caught.
If you like little monsters, then you'll be happy with this set. If not, then save the $40 towards a real figure. If you have Jabba's throne, then these guys will look great -- if there's enough room for all including the Crumb critters.