So I'm into my second cold weather season with these tights, and they are the foundation for my cold weather riding. First of all a comment on the size, I'm 5'9", 145 - 150 pounds, and 32.5 inches in the waist. In general, I wear size L Castelli's, but in this case the mediums are a perfect fit. As JDHP437112 said, these are like a skin suit so don't get them if you don't want that effect and feel. I've worn them down to 28 degrees, at which point I felt the cold but was not affected by it, through the 30's where they excel, and into the mid-40's where I still don't feel overheated by them. I love the straps - the smooth lycra is comfortable, and has plenty of flex to move when I do. It can feel a little tight when I first put them on, but once I get into riding position I don't notice them at all.
So far these have been very durable. All my bike clothing goes through a delicate cycle with a little detergent, then hangs to dry, and these still look new as they move into season 2.
And best of all, my wife likes how I look in them, although maybe that's not the bibs.... :-)