Far as I'm concerned, any neoprene (or other insulation) is too much neoprene in a warm weather knee boot, something often inherently too warm for comfort in its most stripped down, bare bones, uninsulated rubber form. The Muck Boot craze came and went pretty quickly in my part of the South.
Here in Southwest Louisiana, LaCrosse Grange knee boots are the standard, but I've been disappointed with their durability in recent years and switched for some time to Cabela's uninsulated "Scent Free" model to get a bit more comfort in terms of better air circulation with their slightly wider ankle cut, but not much better longevity. Now I'm trying and, so far, happy with the poor boy version of Le Chameaus:
http://www.amazon.com/Le-Chameau-Co...=sr_1_6?s=shoes&ie=UTF8&qid=1332769857&sr=1-6
The ankle cut is wide enough to make them the best ventilated and easiest on and off of those I've mentioned, but not so wide as to make keeping them on in gumbo an issue. I've worn them virtually daily and crossed a lot of rice field and other bad ground in them, but I've not had them long enough to see if their natural rubber will, in fact, significantly outlast the gone-to-hades synthetic compounds most others now use. Time will tell, but "so far, so good"...