This may seem obvious, but I felt exactly the same way about OSX on the MacBook Pro until I upgraded my RAM. I was running at what I believed to be a respectable amount of 1GB, but it was not until I upgraded to 2GB that I felt I was satisfactorily running the OS at top speed. Now, this is entirely unnecessary, especially since Gentoo Linux on the MBP is ridiculously fast and functioning, but I needed it because I do live audio performances in OSX.
If an extra 50 bucks or so is not a problem for you, then you may want to consider getting an extra gigabyte or so.
If an extra 50 bucks or so is not a problem for you, then you may want to consider getting an extra gigabyte or so.