Bought a Samsung Galaxy Tab a month ago (if fact, I sold my Archos 5IT because of it).
I use Aldiko 2 and the Kindle App mostly. Also a PDF reader and Zinio. Is reading as good as my DX or Sony 350/650? No - they are easier on the eyes than the Tab.
Is the Tab giving me eyestrain? No, its fine and I use it a lot of the time. It tends to be handy and it has other apps that mean that I have it handy. I can happily read it for hours. It is no worse than the Tablet PC's and its ergonomics are very good (swipe, touch etc.)
Very pleased with it,
Ross