I currently own 3 WM sleeping bags and really like them all. I went looking for a 30 degree, ultralight bag several years ago and ended up choosing the WM Caribou as it was the lightest bag I could find that would work for my 3 season trips and accommodate my 6'5" frame and wider shoulders. I was hoping to get the HighLite, however, when I went to the store to climb in it, I found the 59" shoulder girth way too light.
Caribou's 35 degree rating has ended up being a bit too cool for me when I'm at altitude and the temps are near freezing, however, I am a cold sleeper. My suggestion is to climb into as many bags as you can and buy as good of a bag as you can afford as it will last you a long time.