I use an iPad mini + Google Drive for Oreilly/Manning books + Goodreader (app).
The iPad was a gift and I just started collecting pdf books. I also use the Amazon app whenever I purchase ebooks from their marketplace. This allows me to stay versatile and automatically sync all my notes, etc. remotely.
+1 for Goodreader. Such a usable app. You'd think a pdf reader is a pdf reader, but there are many small features and UI niceties I would miss if I switched from Goodreader. I wish there were something as good for Android.
On Android (and jailbroken Kindles) Koreader (open source on github) does a decent job of reflowing even 2-column PDFs.
The iPad was a gift and I just started collecting pdf books. I also use the Amazon app whenever I purchase ebooks from their marketplace. This allows me to stay versatile and automatically sync all my notes, etc. remotely.