Very easy on off pack. Large enough to hold rain jacket, pants, hat and gloves. Easy to move from bike to bike. Access without getting off bike. Very water proof so far. I carry tools and tube in tool bottle and with this bag for clothing and food I can quickly move to any bike. Eliminates saddle bag for me on most rides. Light, no rack system for needed gear.
I attach this to the front of my Ortlieb handlebar pack to carry small items that I want quick access to...camera, first aid kit, jacket, etc. It carries a LOT of things, but be careful not to overstuff it or it won't close all the way. Also be careful not to weigh it down too much or it can rub on your front tire and quickly make a hole (patched with Tenacious Tape).
I like that it hangs just below my handlebars and doesn't block my front light. Perfect size for my rain jacket, cell phone, sunglasses, snacks and other extras.