Since devices have gone to glass capcitive displays I dont bother with screen protectors. I have not manged to scratch any glass dislay I owned. But I did buy a used ipad where someone managed to scratch the glass. For the body I like protection, all my devices always look new when I get rid of them too.
In regards to soapy water installs, I have done a few with non removable batteries. Its never been an issue. I try to be a little sparing on the water and try to blot up any drops around the edges very quickly. Most devices have a very good seal around the edges because they don't want dirt and oils getting between the touch layer. It is scary the first time, especially when its a 3G 64GB ipad. I have not seen the NCs screen edges and the bezel does look loose but I would not be afraid to do mine. Just give it over night in a dry environent before you turn it on again. I do prefer the harder plastic screen protectors that go on dry, fingers and stylus' don't drag but they do get scratched and have to be occasionally replaced. For me, I like my screens bare naked.