I have a pair of the knee high rubber boots with 1000 gram of ultra lite thinsulate and they have worked great for me for the last 2-3 years. I wear them even when the temp. gets down to around 0-10 degrees and they seem to keep my feet warm with a pair of heavy socks on.
Overall I would say they work great for the money. Why pay $30-$40 extra for a name? Sometimes that is all you are paying for, the quality is the same.