My wife & I have the older and newer WM Ultralight. They are both good bags and the newer one with the draft collar is very nice.

Just a comment about temp ranges. People have mentioned that what is comfortable varies from one individual to another, but you should also be aware that it varies from day to day for the same individual. About 3 years ago in January in the Grand Canyon I had the toughest solo hiking day of my life. I was wiped out when I crawled into the bag about 10:30. Temps didn't get down to freezing and I was definitely cool all night even with longies and fleece and down jacket. Not so uncomfortable that I couldn't sleep, but definitely on the edge. The next night, at higher elevation, the temps got down below freezing and I was warm and toasty and didn't need to wear as much. Same bag, but a completely different set of physical parameters -- early vs. late start, half the mileage, 1/3 the elevation change, leisurely pace vs. really pushing it, well hydrated and fed vs. going to bed on empty.

Based on that experience, I would say that my physical state created a 14* variable in the "comfort range" of the bag. The first night the thermometer in the campground showed a 34* low and the next night, my tea bag froze solid and I have no doubt I could have been warm down to the 20* rating of the bag.

Your sleeping bag is arguably a critical piece of survival gear (don't we need to survive every day?). When you are "out there" you will absolutely not care about whether you saved $100 if you are not comfortable. Poor sleep and hypothermia are classic predecessors to outdoor tragedies.

One further comment: Going out into the yard from a warm house after a nice supper and a day sitting in the office to "test" a sleeping bag is not a valid trial -- or at least should be taken with several grains of salt. Personally, I would add about 10* to the rating of the bag based on "yard testing".