Arm warmers, leg warmers and knee warmers are all absolutely essential bits of kit, especially for the commuter when conditions change during the day.
They're perfect for just so many circumstances, especially in the uk when weather is so varied from one hour to the next.
It's all very well having dedicated long sleeve jerseys, 3/4 and full length tights, but what happens on those days when the clouds disperse after an hour of riding and then you're then too hot for the rest of the day? Lightweight, easy to store in a rack bag or jersey pocket etc
I've got the dhb roubaix ones and they've been excellent.
The only downside is that it's essential not to let the other half walk in on you while preparing for a ride at the moment you're only sporting the arm warmers and leg warmers. Unfortunately they have to go on first but it looks bloody weird!