the Glove Lock system was the first thing I bought after I bought my drysuit - right after I tried it out the first time in 40-50 degree water. It's worked fine for me, but I really don't have much to compare to. As others save said, the rings seem large, but I don't really notice them while diving. I do tend to notice them while putting my BCD on and off, and that's probably more just from there being anything there to snag the harness, not necessarily a size thing.
Leaks were always user error - usually getting the glove liner caught in the seal. I've learned to fold the inner glove liner down so that it doesn't interfere. I keep meaning to pick up a pair of the Pinnacle Merino liners to try.. I keep the inner seal in place - if I'm using undies with thumb loops, I use them to create an air gap. If not, I use tubes of some sort.
Initially I set up the blue gloves into the rings with a lot of extra "sleeve" still ( not wanting to cut things that couldn't easily be replaced). I finally shortened the gloves up by several inches which really made a difference in donning them.
When removing them, don't completely remove one glove before doing the other. Loosen both bayonet rings first, then start removing the gloves - the extra grip from the glove helps a lot.