Here's what worked for me, after much messing around. Note I have root access to my Linux/Apache server, so I can run chown commands. In shared hosting environments, you'll simply have to ask your tech support to do this. Shouldn't be a big deal.
directory - permissions - owner/group
wp-content drwxr-xr-x (755) apache apache
uploads drwxr-xr-x (755) apache apache
themes drwxr-xr-x (755) casey psacln
...so that I can modify my theme with my FTP client and text editor of choice. If themes was apache apache, I would not be able to edit my template(s).
This works fine, and I can upload/save/delete at will with the WP 2.7 Flash uploader.
PHP safe_mode is ON.