Stewy,
Go to the Danner outlet in Portland and get yourself a pair of either their felts or their studded felts. They are by far the best boots I have ever worn out of the 4 pairs I have owned. THe synthetics always end up cracking (even the high-end weinbrenners. Put a thin coat of Aqua seal over the stiching on the Danners. Their only weakness is the stiching. I've had mine for 5 years and have feplace felts on them several times. THey are totally bombproof IF you aquaseal the stiching. I have many friends who guide in AK and ID who also swear by them. At the outlet, they cost $99.
Have one friend who has the Teeney zip-ups. He only uses them in the summer and then only when he wet wades. Said the support of the Danners is superior to his Teeneys. He doesn't have many days on them and has also commented on whether or not they'd hold up to heavy use. I love the Danner, and as stated above, just get them wet before you slide them on.