PDFs are, of course, the worst possible choice of formats for eBooks because they are created for a fixed page size and don't "re-flow" like "real" eBook formats do. With a bit of reprocessing with various free tools you can download from this forum, my understanding is that one can achieve adequate results for PDF display, but that's one area where the larger screen of the iLiad is a big plus. General advice is to avoid PDFs like the plague if you possibly can.
Build quality of the Sony is generally excellent. Very, very few reports of problems.