RAM won't really affect bootup time. During bootup, your Mac is putting all of it's effort into reading the hard drive, and talking to every hardware component in your computer. 1gb of RAM or more will ensure RAM isn't limiting your computer's bootup time.
RAM affects how well your computer behaves when it's actually booted up. Unless you have fast-user-switching enabled with two or more user accounts, or are using something like Logic, Final Cut Pro or Aperture, I would expect there to be much difference between 2gb of RAM and 4 gb of RAM.
I run 2 gb of RAM in both of my Macs and never really find it limiting, even with quite complex recording projects.
RAM affects how well your computer behaves when it's actually booted up. Unless you have fast-user-switching enabled with two or more user accounts, or are using something like Logic, Final Cut Pro or Aperture, I would expect there to be much difference between 2gb of RAM and 4 gb of RAM.
I run 2 gb of RAM in both of my Macs and never really find it limiting, even with quite complex recording projects.