Is it really necessary to upgrade my macbook to 4 gigs of RAM? I have 1 gig in my macbook right now and I can't decide whether to upgrade to 2 gigs or 4. Will I see a lot of benefit if I upgraded to 4, or will 2 be sufficient? When I'm multitasking in iTunes, Safari, dashboard, etc..my free ram is only around 20 megs. Also, will applications launch faster with more RAM? Or is this limitation due to the speed of the Hard drive? Thanks!