These bottles,
Are you/Did you encounter any problems as many of the BB users are with the air being sucked through the stopper when lifted due to the stretching effect?
Nope. No problem at all. They are way to rigid (and not clear [I must have mentioned that somewhere along the lines]) and you could stack them on top of each other...full, if the airlock sticking out of the top wasn't in the way.
It reminds me of a big lego block come to think of it.
Also with the Vittles Vaults (opaque too) you could get your whole had in them to wipe them out to clean them...even though you don't need to as I just soak them in Oxy for a week or two while I rotate in one of my other ones (I have 4 and rarely have more than 2 filled at a time)
If there is a stubborn mess or I need them faster I just use my old Carboy Wand I got from somewhere. It's basically an attachment for my hose that makes the end jet out in several directions and can knock loose just about anything there.