I have the kobomini, which has the no-glare screen with eInk. It's easy on the eyes reading wise, in direct sunlight or shade, and all I really wanted was something compact but highly readable to transport a bunch of books without the bulk. It has WiFi, but the only time I've ever used it is when I'm lying in bed and my iPhone is out of reach. I use
calibre to convert books I've downloaded in different formats into ePub's, and I've never had any major problem transferring various content from other formats if I convert them this way. Occasionally things are just slightly wonky if converted from another format, but not in a way that makes reading impossible or anything, just a bit of odd formatting or spacing on occasion, though usually it's surprisingly smooth, and considering I never see the files in their original formats, it's entirely possible that the formatting problems occurred in the original versions before conversion.
edit: Because I'm still friends with my old boss at the used book store, I find I tend to fall back on reading printed books more than I expected. It was only after writing this post that it occured to me that the big, bulky book I'm reading now is probably available for download, and it is. Since I paid for the printed version, I feel no guilt in downloading it so I can have a portable version, which means taking only the kobo to the hospital with me, instead of lugging around four books.