I've had my Libre for a week now and am pretty satisfied. I've read, I think, about five novels from the public library and I've played with it some loading my own writing in different formats. I like epub because I can have my own fonts, but epub for some reason does not allow the 'find' function. I figure if I need to read something (non-DRM) that requires me to use the 'find' function, I'll just load it in that format -- so the versatility of formats is appealing. I've tried PDFs and the result is a mixed bag -- it works best if I create my own PDF's at 3x3.3.78 inches. I tried out music playing but I don't think I'll use the reader to listen to music... when reading I prefer my music a bit further away from my ears, and if I really just want to listen to music I have a player for that. The battery charge feels reasonable -- the low battery alert came on after I'd read about two or three novels, in the midst of a really fat one -- and I was able to finish it without having to recharge. I had to use the reset button only in the first few days, and I think it might have been because I wasn't fully sure what I was doing -- also, at that point I only had the internal memory but after getting an SD card and loading my books there, I have not had to use the reset button even once. I took my Libre to the laundromat yesterday and I was thrilled to read books in the bright sunlight (the sun was out after days of cloud and rain) and inside.
I don't know about the 505 or the Kobe, but the Libre works for my needs.