Nice upgrade, I started about 9 months ago sleeping a hammock and love it. My back has never felt better. I sleep in it every night and If you keep it stretched tight, you will not have as much issue with the knees being over extended. Its also pretty comfy to just pull your legs up a bit and sleep with knees bent. At home every night I use a old sleeping bag rolled up under my knees and it keeps them from over extending. As for cold weather, I have a military bag that is intermediate cold rated and I spent five nights out this winter at 5 degrees or less and was toasty. Find the wool liner, which can be suffocating, so I opened the seams on the side so I could move my arms a bit more. Then I draped a wool blanket over top of me yet. Better yet is to get the extreme cold surplus bag and no blanket or liner needed. I think once you get it going, you will absolutely love it, never go back to sleeping on a cot or the ground.