A friend showed me his HH ULBA several years ago. I'd previously seen older HH products but wasn't impressed, but this time, the low weight, small size, and relative comfort compelled me. I've been using one for some years, and developing a replacement (to be described sometime soon).
Having a lean and bony body, I don't sleep well on hard surfaces. Comfort and the greatly increased range of possible pitching sites are the primary reasons that I use a hammock (rather than a comparatively small/lightweight ground shelter).