I have a Glo Toob, but I have the one that takes a tiny 12v alkaline battery. It's intended use is as a marker, not an area light or flashlight. It's good for things like marking your campsite so that you can find it at night. It's basically a durable, LED version of the ubiquitous glow tubes that contain chemicals that you bend to activate. It is well suited as a marker and has no peer for that purpose, but it's not a flashlight or area light by any stretch of the imagination.
EDIT: I should qualify that by saying it's possible to use it as a light in a tent to read by. but I have never personally tested it in this use. My advice comes from my experience using the light in other circumstances. YMMV, as it depends how big your tent is, what color it is (for reflections) and how good your night vision is; it's not as bright as a lantern, but still gives off light.