I use this glove at temperatures of 50-60 degrees Fahrenheit, when a heavier glove would be too much, and fingerless glove would not be enough. It's just right for that use - comfortable, stops the wind, keeps your fingers warm.
These gloves are very thin and provide great feel on the bars. For the first few minutes in 40 deg dry weather, my hands were cool, they then warmed up like magic. I was so impressed I bought a pair for my daughter. I plan to bring these along in summer for long mountain descents (we were going to have a several thousand foot descent starting at 10,000', maybe next year).
I've been looking for a full fingered glove for days when half fingered gloves might be slightly too cool for the fingers to be comfortable. This glove was a good choice for me......The sweet spot seems to be 48-60 degrees, but you could probably stretch the range a bit and still ok. Fit is similar to any other Castelli short to long fingered option.