Ehh no. FF has way too many awkward keyboard shortcuts that are not integrated to the rest of the OS, whereas Safari is simple. cmd+t for tab, cmd+q for quit and so on. Safari executes JS much faster, you've seriously got to be kidding me.
Ehh... Firefox has the same hotkeys that you mention here (cmd-t, cmd-q). Basically, firefox has the same hotkeys as Safari, with the notable exceptions of Back and Forward and cmd-?. It then has cmd-k to go to the search bar, and the smart search bar that blows Safari away for keyboard accessibility. Now, Safari is slightly...slightly...faster than FF 3.0 when it comes ot JS rendering. But FF 3.1 implements a new JS JIT compiler that is much faster even than Chrome. These benchies don't have Safari on them, mainly because Safari is in a different universe of speed than either of them. SunSpider, btw, is a benchmark developed by Apple.
And you know what, even if FF actually was slower (it is not), I would still use it for a thousand different reasons, that are collectively called plugins. Safari can never match FF for that simple reason.
By the way, FF scrolls great for me, not sure what's up with your system.