Look, I have never been in a coma, but I have read/heard a lot from people who have been in coma.
Some say there was nothing, just blankness, same as if you got a body-general anesthesia, you just turn off completely.
Some say it was a terrible/hell experience. I don't really know why they say that, if it's because of the overall experience (sleeping for two weeks and then waking up out of nowhere, with your body feeling weird because you haven't moved anything for weeks, surely would feel bad/weird), or if it's because they saw something middle coma. I highly doubt the second one because, well, you're in a coma.
But don't get conclusions from what I've said tho. Wait for more experienced people to comment about this. In fact, I just want to add to the discussion saying all that I know about this. It's not much, but, I hope it helps on something.