Pero,
I have used e-ink readers for over 10 years now and I currently use a Kindle 3G for my reading. I love it and it is the best reader I've owned mainly because of the big catalogue of books on amazon.com, open for non DRM materials and excellent battery life (I basically charge it once every three weeks).
Now the bad news: it is not great for scanned pdfs, non of the e-ink readers I've seen are. Text is OK, but the moment you have graphics (in my case electronic schemes or flowcharts) it becomes a problem. One of the big problems IMO is that a scanned A4 page has to be compressed in size a lot in order to fit on the screen.
If you want you can email me one of your pdfs and we can go for a coffee and you'll see how it looks on my kindle.
For pdfs I use my iPad, the resolution, colors and fast and intuitive zoom/navigation controls are ideal for this. Of course it also has it draw backs (price and battery life) which is why I am not getting rid of my kindle anytime soon for pure reading.