I work outside in the southern US, and though it doesn't get as cold as up north, we are presented with a different challenge.  It is touch dressing for 40F weather that turns to 65F in a matter of hours.  I hate wearing jackets and would prefer to wear an extra layer, which is where this ColdGear comes in.  It fits nicely and is not too snug like I find most of the compression type shirts.  It does provide decent warmth down to 50F to 55F, but below that and a jacket is needed.

I've also found that it can get uncomfortable and itchy along the arms if worn for more than six hours or so.  I have found that putting on a moisturizing lotion decreases the itching quite a bit.  But wearing for more than ten to twelve hours can still get a little uncomfortable.  And since I work twelve hour shifts, the last hour or two can make you feel like you simply have to take this off to get some relief.