I have the Kobo Touch. I have downloaded a few books from my local library website. Most viewed and resized fine. I did however have an issue with one book where the book font looked fine on ADE but showed up as unreadable symbols on my Kobo. I tried to resolve with the library but because it read ok on ADE I think it must be an issue with the way Kobo read that particular file. The thread on my issue is here
However, I think it was probably a one off as I haven't had problems with other books from the library.