IMO rubber boots suck.
Pick up a pair of rocky's or irish setter's... get one that has some removable inserts (so you can add then in for when it gets cold)
if there is a lot of water in the area your using them in use some of the new water repellant stuff that you can get at home depot / lowes.
here's a video, called neverwet... getting some great reviews all over on this stuff.