Hello gadetra! Welcome to Mobileread.
I have PRS T2 and its my first ereader. So, I'm also new to this e-ink world.

But I guess I can share what I feel about my T2.
Yes, your fears are right and you can't read a thing in no light. But then you can always use lighted covers or any other source.
There's a library option in applications but I haven't used it because none of the libraries in my city offer ebooks

Sony is great with note making and you can transfer the notes to evernote. You can highlight the text, refer dictionary(quite handy), and you can feed in notes via handwriting or keyboard option.
I don't know about kobo but T2 is fast enough to not give you irritation of waiting.

Sony is certainly better than others in handling PDFs as its got landscape mode which kobo doesn't have, I guess? BUT this doesn't make it any good. PDFs are readable but don't expect much from landscape mode as it will only shrink the text horizontally and you will find normal mode much better. Again, I'm talking about PDF whose text can't flow! And be it landscape mode or normal one, increasing font size will not at all work with non flowing PDFs.
But the solution is that you can convert the PDF into epub and calibre will do it brilliantly. But you may have to bear the broken lines. But then it will not hurt.
Sony lacks somethings but then you have the alternatives.
And, I too had this region problem with nook but someone told me the trick that you can register it on B & N by giving an email address and skipping the credit card details. And, it will work fine then. But I chose sony as it was faster than nook ST. I'm not at all patient you see.
Again, I have only used T2 so can't say T2 is better than kobo.

All the best with whatever choice you make. You will not regret buying any of them hopefully.