Rating: 5 / 5
I just tested my Western Mountaineering Megalite summer bag last night in my backyard here in Henderson, NV (Las Vegas' southern suburb). It was a chilly 22F and I soon learned the bag would handle this temperature as long as I did my part, i.e. wearing thin polyester long john tops & bottoms, hiking sox and a thin balaclava. My tent was a TarpTent Contrail which was "airy" and did not give much, if any, additional warmth.
Also I used my ultra light, full length Thermarest. Again, no problems.
The idea was to see if I could use all these items on a High Sierra trip that might have sub freezing temps. The answer was "YES".
The Megalite is great for summer camping here in the Southwest high deserts where cold temps are often encountered in early and late season camping. It's full length, dual slider zipper is great for hot evenings that turn into cool nights. Simply unzip from both ends and the top stays over you, being held in the middle by the sliders, but you have excellent ventilation and you can "hang a leg out" to cool down. If the temp drops after you fall asleep just pull your leg in B/C the top is still in place, held by the mated top and bottom sliders.
The Megalite has 850 fill goose down. Just about the best available. With no side baffles you can shift down to the bottom or top, depending on your need. And, once you're laying in the bag, the down stays put.
It has plenty of room inside. Great for hot nights or for room for extra insulating clothing if needed, which is why I bought it and am willing to carry a few extra ounces. This versatility, along with the outstanding quality, makes the considerable investment well worth it.
And one final thing. That "Made in USA" American flag sewn on the foot of the bag is a nice thing to see, especially on such a well made piece of gear.
2 Year Update: Still my 1st choice for summer/3 season camping. For hot nights I unzip it all the way and use it as a quilt W/ teh foot end hooked over the end of my full length mattress.
3 Year Update: I used the Megalite at Arapaho Pass, CO, in October in teen temps. I wore my Thermolite insulated pants & top & was very comfy W/ no feeling of being cramped for space. As I suspected, this bag's girth permits this versatility.