I love the Alpinlite; it has just enough more girth over the Ultralite equivalent that it fits me well, and doesn't compress my down jacket or pants when I wear them in the bag. I've done that, and it let me sleep cozily warm on a zero degree night last year.

The double draft collar (front and back) is a real treat, though the extra drawstring takes some getting used to - nearly choked myself when I thought was tightening the hood.