In the mean time they have made it substantially more difficult to configure the rejection of cookies.
Jesus... I'm actually thinking IE is better at this point.
Pay no attention to Firefox's built-in cookie-handling interface; it's designed for Joe Kegger — not computer nerds and/or privacy control-freaks. Get whatever cookie-handling plugin(s) that'll give you the level of control you need.
Another cookie plugin I like is Self-Destructing Cookies, which provides "delete-on-tab-close;" "delete-on-browser-close;" and "never delete." Unlike CookieSafe, however, it lacks a function for viewing the complete rule-set — only the rule in use for the currently-selected tab's domain.
* If I remember correctly, there's a different version or branch of CookieSafe that's incompatible with recent versions of Firefox, plus a "Lite" version that's little better than Firefox's built-in level of control.