I use these shoe covers in temperatures between 35-50. They are easy to put on and fit nicely. Not quite as warm as I had hoped and a tear developed within the first month of use near the Kevlar seam on the sole of the cover.
Kevlar trim on the bottom of bootie has shredded and come un-stiched after two months. My last PIs lasted several seasons. Guess I'll see if duct tape will get these thru the winter.
These Pear Izumi booties replaced a pair of neoprene covers which finally failed due to a torn zipper.
All in all Im reasonably impressed with how well these new ones work. Entry and removal are much easier due to the two Velcro-like fasteners on the back. The covers have worked great in low 40 degree temps while wearing alpaca or wool sox. One thing I have finally learned (which no one ever shared with me) is that circulation trumps insulation. Leaving ones shoes looser in the winter in concert with a good set of shoe covers does wonders in keeping those toes more comfortable.
Thanks to a spring triathlon, I need to do serious biking through the winter. These shoe covers are a lifesaver on those cold, windy days near freezing. Cannot believe I put off buying them. Highly recommended.