I recently acquired the Altos 20+ bag and took it out for a week long trek along the Highline Trail of the High Uintas last week (Aug 2016). Temperatures got down into the mid 30's a couple nights, causing us to wake up to frost all over our camp those mornings. I paired the Altos 20+ with the Altos insulated air pad, also from Teton Sports, and I was comfortably warm every single night. I did not even have to zip up the bag the whole way or cinch it up at all, so I have no doubts that the Altos 20+ could hold up just fine in temperatures down in the 20's with it zipped up and the hood cinched down. This bag is supposed to be EN rated down to 20, meaning it really does have a comfort rating (not a survival rating) down to 20 degree, and I think this bag really delivers on that.
I'm 5'10'' with a slim body and had plenty of room to twist and turn without having too much extra space. I'd say anyone around 6 feet with an average build would be comfortable with this size bag as well.
I also had no major problems with zipper snags. As with all bags, you just have to be careful and gentle with it to avoid the snags.
Not only is this bag nice and warm with great loft, but it also is very light and compresses down very well. Without the stuff sack, it is a little less than 2.5 lbs. Even with the stuff sack, it all came out to be only 2.45 lbs on my scale. I usually don't take stuff sacks, but with this trip, I did because it was essential that I compress the bag down as much as possible to free up space in my pack for all the food and other gear I needed for the week long trek. I found that I was able to compress it down to about 8 inches by 8 inches by about 9 inches or so.
One last thing to note is that I had no problems with down leaking. I saw no more than 2 to 3 stray feathers that escaped the whole trip. My other hiking buddy who had a North Face down bag said he was waking up with quite a few feathers all over him every morning. And while I plan to take great care of the bag and do all I can to keep it from ever getting wet, it gives me an extra bit of peace of mind to know that the MTN DRY treatment of the down will enable it to still loft and maintain some insulative properties should it ever get wet out in the field.
Overall, I think Teton Sports hit it out of the park with this bag, given the price. I think anyone who bought this bag would get great bang for their buck for typical 3 season use.
Disclosure: I received this bag for an honest and thorough review.