The trick with the new 2 button ones I've found is to remember to turn them on before you ride off for your journey. Adjusting the heat setting is not too bad but holding one of the buttons down for 5 seconds to turn it on with winter gloves on can be quite tricky!

I've found them handy in the current weather, certainly find in around freezing temperatures with some small hand guards to deflect the wind and intermediate weight gore-tex gloves