I like them, so it must be wrong....

I use them (Freestyle AP, 1 ltr) for my C41. I go through shooting peaks and valleys with this stuff, and my chems don't get used for 4-8 week stretches. These bottles work well at keeping the air out and being submirged in a warm watter bath (when time to get used). I've only had one falure and I'm pretty sure it was due to not using the stuff for 6 months.

I notice no thinning of walls or air leaks. They work fine.

The only other chems I use are WD2D+, Rodinal, HC110, Stop and FIX. These do not need anything special. I just use regular bottles.