My Sony 650 has never rebooted itself, and I can't remember any bugs in it. Once in a while, some epub that I created myself didn't load right. I don't think it's ever had a firmware update. There are some steps I have to take on the computer in Calibre, before loading the book (to get the fonts to look better, etc), that I would rather do on the reader. So, the firmware is simpler but bug-free.