I've only used these in temps in the mid 30's so far but kept my hands warm with the inserts and w/o the inserts. Can't wait to try them in colder temps, with a heat pack inserted between the liner and shell I'm confident they be effective in much colder temps-will do a follow up review this winter after some skiing and snowshoeing outings. The construction of the gloves seem to be top notch, after all they are made by Outdoor Research. One thing to take in consideration is the sizing-I normally wear a size large but had to get these in XL.
This review was written in the old system and had content requirements that are different than reviews written today.