Unlike Shawn above, I get cold pretty easy. I got one several years ago as a gift and wouldn't be without it now.
The only problem with the idea, is you will need to hang your bow and zip it. Some guys stand and hold their bow for an entire hunt. I'm not that hard core. I place my bow in my Lone Wolf's bow holder with a nocked arrow secured with a holder, zip and sit down.
In order to make a shot, I then have to stand, unzip, and pick up my bow. Sure, I've missed some opportunities because of that, but I figure they are offset by the extra ones created by spending more time on stand.