I agree completely with Sam - the default should be the automated updates like Chrome, with an option for those who care and have a process for controlled rollouts for large IT departments to control for corporate environments.

On my personal PCs, I find the Chrome model very nice, as I don't ever even have to care about it, the updates just happen and I'm golden.  Firefox is just annoying with the constant prompts for update which require a browser restart, which of course open a page indicating what changed - I typically don't care what has changed, just do the update and be done with it.  The addin update procedure on Firefox is even worse - popup, followed by a browser restart followed by another popup.  Grrr.  That is one of the reasons I rarely use Firefox anymore, and once IE9 is finally released I'll likely retire Firefox as my secondary browser for these reasons alone.