It's a tube! It does everything a tube should do, and does it well. To me, it represents a fair compromise between weight and durabilitypuncture resistance. I like the choice of valve lengths because I saves me from using expensive and troublesome extenders. I've never had an issue with one of these tubes, so by default it has become my go-to tube.
I use my bicycle primarily for suburban and city commuting, doing an average of 90 miles per week and replace about one tube every 3-4 months, due to punctures from glass, staples and other sharp objects. I do ride with patched tubes for as long as I can get away with it. Durability depends on the amount of construction and other debris in parking lots and on the roads I ride, which varies seasonally. These tubes have proven more robust than any of the others I have tried.
The tubes are easy to install and I have typically had good results with Conti's tubes but for some reason, had three or four flats in rapid succession with these. It may just be the time of year with lots of extra debris on the roads. I have loved their 700c tubes and don't see any reason why their 650s would be different.