I know there are a real lot of IBtanked fans, but since I discovered the UDCT, I don't even consider an IBT anymore, I love the "goof-proof-ness" of that locking ring. And one other factor: some folks in the vv3 thread were talking about those carto-filling funnels, and I coulden't figure out the point of them, since it's pretty easy to push the carto down myself and fill with a syringe, but it was explained that those funnels save wear and tear on the o-rings from the edge of the carto. So I had a good look-see at the UDCT, the next time I had to replace the carto, and do you know, the only o-rings in the thing are the small ones that seal the carto, and in the UDCT, those are surrounded top and bottom by the metal flanges of the caps -- you'd have to be pretty spastic to do any damage to them, even with pushing the carto up yourself. So I think the UDCT saves whatever trifling price those funnels run -- at least, if one is careful and doesn't try to push up the carto like a gorilla in a china-shop. And also considering that I found the UDCTs at Vapor Kings for $6, replacing a UDCT if the o-rings were damaged wouldn't be a major expense -- I can certainly understand not wanting to damage an IBT, considering what those things cost!
Andria