I bought a pair of Simms water boots a couple of years ago, after reading endorsement in our forums from fish-pros about how much they liked them. When the people who have wet feet four or five days a week talk about gear they find holds up, I listen.
I can't tell you how many pairs of cheap ($30-$50) boots I've bought that only last a year or two before falling apart. They're just not made to handle being wet so much. Or darter shuffling. And I don't get out collecting all that much.
The Simms are expensive, but well worth it. Cheaper in the long run, because they last. The RipRap that Joshua described in the previous post looks great, but I went with a heftier boot that offers more toe protection and ankle support. I think I'll put the Rip Raps on my Xmas list.