i have the g4z as well, they are great! i also have the simms g3 guide waders and pretty much the same as the g4z minus the upper part.
i will stand by simms and will always only buy simms gear especially waders. i have had my g4z for two seasons now and have over 100 outings on it with hiking and what not and still have yet to have a problem. i prefer to wear my g4z over my g3 guides. they are so damn comfortable.
i even wore my g4z on +30 days on the water and remarkably they were not that hot at all.