The recent nightlies are very broken. Stick with the 0.8 point release for now, unless you can get someone to recommend a non-broken nightly. I'd recommend one, but I forgot which was the last good one.
Firefox launching time has never been better than Safari's, and I don't think it ever will be. Its speed is in rendering, especially over a slow connection (at least in my experience).
You can keep tabs on the nightly build progress at
the Burning Edge.