The Thermolite is overrated in my opinion. I've used mine in winter and summer and it kind of failed at both. As a liner, it added maybe 5 -8 degrees to my bag. I generally sleep warm and have lived in cold climates my whole life, including working outside in sub-zero temps on a regular basis. The liner really added very little to warmth, far less than wearing my down puffy or a fleece jacket to sleep in. As for the tangling issues, we won't even go there. Suffice it to say, after one midnight bladder relief session, it ended up outside the tent and stayed there. As a summer bag it was OK, but on a 60 degree night I threw my rain poncho over me to keep off the breeze enough to sleep. That happened twice, so I'm a little leery of using it again when temps could be a little cool. I've been eyeing that woobie and they look like a much better solution for a winter summer dual purpose item.