According to WordPress developer Ryan Boren, the most requested WordPress feature is tentatively slated for the as-yet unscheduled 2.7 release.
This already exists in the form of a third-party plugin, which I’ve actually used successfully before on another blog. I’ve always found upgrading manually to be easy and problem-free, though incredibly tedious. Because I don’t use many plugins or alter any core WordPress files, I think automating the process will be a safe option for me, one that I’ll trust more in the hands of the core development team. Still, I’m sure I’ll wait till it’s been thoroughly tested in a couple versions before using it on this site.