I own one and really like it, but it depends on where you will be and when. I found it fine for summer camping at low altitudes in the lower 48.

I am a warm sleeper and found it to be good for well below the rated 55 degrees (I can sleep just fine with only a sheet at 55F). I found it comfy in the upper 40s and just OK in the mid 40s. Range can be extended by adding some clothes either worn or piled on top of you.

My daughter has used it as an inner bag to extend the range of another bag. It seemed to work OK in that capacity, except that she didn't find it added enough in some of the conditions where she tried it.

All that said people vary widely in what they find comfortable, so YMMV. If you tend to be cold and will camp where it is chilly it might not work out.