I have resisted this upgrade because I read many horror stories about problems with mail. I use mail fairly heavily. I have an enterprise e mail account and a gmail account. I use the combined in box feature quite a bit. The enterprise account pushes e mail and calender changes to me (also on iphone). I use "Attachment Tamer" and like it. I also use firefox. I use microsoft office for mac. I use time machine to a time capsule. Should I expect troubles with Mavericks or go ahead and upgrade? Can I go back if it is a problem? I have a new macbook pro retina and currently running OS 10.8.5. Any input most appreciated.