I have a 1st gen Kobo Glo, and it renders PDF files pretty well.
I have to say that I don't usually use my ereader with PDF files, a 6 inch screen is really not the best way to read an A4 sized page, but the text is readable and clear, albeit small sized.
I can't test this with more recent Kobo devices, but being more or less the same firmware, the experience shouldn't be very different.
A couple of pics, so you can judge by yourself (the actual rendering is a bit sharper, the slight "blur" is caused by the photograph, not by the device).
