As everyone else is saying, better than nothing, so not completely useless, but in no way to be confused with a proper large softbox. You'll still be better off taking the flash off-camera rather than leaving it on-camera. You will still get an edge to your shadows. And there will be a hotspot. But if used in close, it can be worthwhile. I use a cheap eBay ripoff of the Lastolite Ezybox Speed-Lite, a small 8" softbox. It differs from the Lumiquest in that it's deeper and shaped more like a traditional softbox, and has an inner baffle as well as the outer one. It's a PITA to set up, and doesn't fold quite as flat, so you are giving up convenience over the Lumiquest. I far prefer (if the venue allows), bouncing with van Niekerk's Black Foamie Thing, for quality of light, cost, and convenience over using the small softbox.
Here's a shot I grabbed at Comic-Con in the huge hallway at the front of the convention center (that's Mike Carlin conveniently mugging for me with Karen Berger), with this softbox.
5DMkII, 24-105L @28mm, iso 400, f/6.3, 1/160s. Shot from 5-6' away.
YN-560(MkI) inside softbox, triggered with RF-603s, held in left hand overhead, ~1/4-1/8? power.
As the ceiling is well over 20' above, there really weren't any bounce surfaces around to use, and all the moving crowd of humanity that makes you feel like a salmon swimming upstream gives you limited working space, so it's not like you're going to set up a backdrop and stands (although there are folks who do that out back for the many many cosplayers). I had the flash off-camera with radio triggers, but was simply holding the flash in my left hand while I shot with the right. I think I had the diffuser panel pulled out and flopped down, so the flash would be set to its widest zoom setting as well inside the box.