Do eyes get tired from using the Amazon new Kindle Paperwhite (2013)?

Question

PDF

Good afternoon.
Users of this model, tell me, do your eyes get tired from this device (reading mostly in the dark, before going to bed)?
And what about the pdf, is it really inconvenient, or is the devil not so terrible? Reading mainly those literature (initially computer or scanned with superimposed text).
I heard that in the second quarter the third generation of paperwhite with a density of 300 ppi will be released, is it worth the wait or is it again rumors, so you can not buy at all.