Ya the valve on the source took a little getting used to for me but as mentioned above, it only squirts a bit if you have the bladder/pack compressed pretty good. They also offer a different bite valve available for purchase if you don't like the one that comes with it. I know, more money for an already expensive bladder, but it's an option if you need it.
I have not used the universal tube adapter to fill the bladder but I do use the built in quick disconnects to connect an inline sawyer mini filter to a dirty water bladder and fill my source bladder without removing it from the pack. It works pretty slick. This last year was my first season using that system but it was pretty awesome to not remove the bladder from the pack and have gravity fill it while I heated water and let my mountain house hydrate each night. The quick disconnects provide some nice flexibility (I know other brands use them as well).
I have not used the universal tube adapter to fill the bladder but I do use the built in quick disconnects to connect an inline sawyer mini filter to a dirty water bladder and fill my source bladder without removing it from the pack. It works pretty slick. This last year was my first season using that system but it was pretty awesome to not remove the bladder from the pack and have gravity fill it while I heated water and let my mountain house hydrate each night. The quick disconnects provide some nice flexibility (I know other brands use them as well).