I have a love/hate relationship with Muck Boots, I have the green "Edgewater", good support, comfortable, but I find them somewhat "cold", the higher price more insulated ones seem to be built similar except for a foam insert in the sole. The material is supposed to wick moisture up and out of the boot, but the top is tight to the leg, so there is really no ventilation going on.
For temps down into the 30's, you'll be ok, but I'm betting they will be hot in warmer temps.
Cheapest I've found is from muckbootsonline, free shipping, and free returns if you need to exchange for a different size. I'm usually a 10, but the 11 fit better, plus you can fit a felt insole in there and warm that sucka up a little for colder temps.
Oh, they're made in China
Overall not bad, and some folks don't suffer as much with cold feet. Another option to look into is the XTRATUFF neoprene insulated.Made in America, VERY comfortable, I find them much warmer, the boot body is soft and pretty much ankle fit, these are the boots EVERYONE in Alaska wears. You can find them on ebay, the guy gets irregulars that have very small defects in appearance, mine was that one boot was 1/2" higher then the other, otherwise perfect. they also come in non-insulated, they run under half price of retail.