A while back I stopped using kindle and migrated my library to epubs. Apple's ibooks reader is much better and I didn't find much benefit out of eink devices. With ibooks you can sideload your own epubs, so it isn't much of an issue. Adobe reader also has a good reader mode for pdfs. Also I have iCloud library for my sideloaded books, so it's all cloud synced.

The only real benefit of kindle is the library selection and prices. The ereader software itself is mediocre.