>lack of a restart button.
I don't think Chrome has one. Anyway, either press shift+f2 to bring up the Developer Toolbar and type "restart", or install an addon like Restartless Restart (https://addons.mozilla.org/en-us/firefox/addon/restartless-r...).
You can also just go into the settings, and set "When Firefox starts:" to "Show my windows and tabs from last time".
And I don't see why a "normal" user should want a default button in the UI to restart the browser.
>Memory leaks
The situation is much better now, there still are some leaks here and there, but nothing huge, at least with my usage (I usually restart my browser every 1-2 days to update to the latest Nightly, and have about 50 tabs open).
The team responsible for memory leaks is the MemShrink team, you can see their progress here: https://blog.mozilla.org/nnethercote/
I'd also suggest to install the addon "about:addons-memory", and see if any of your addons is leaking memory (https://addons.mozilla.org/en-us/firefox/addon/about-addons-...)
If you still see memory leaks, please report them on bugzilla.
>Cookies
While something like this would be nice, I don't think that "normal users" needs to mess up with Cookies.
If you're a power user, and want to enable/disable cookies on a per-sites base, install an addon that let you do it.
I'm personally very happy with Cookie Controller: https://addons.mozilla.org/en-US/firefox/addon/cookie-contro...