I'm pretty sure they are fairly realistic. I once had one by accident, me riding on a motorcycle chasing a thief, and I could feel everything normally, although my vision was distorted a bit. Anyways, me and my 3 friends have been studying the brain lately, and I think, from the information I've put together, as long as you concentrate on your dream, everything will be pretty realistic. (I'm not saying focus on the fact of dreaming ITSELF, I mean if you want it to feel more real, then think about what your doing, but not too much, that will wake you up!)