@gussnarp sorry to be the apparent bitch in this thread
I think that all the components weigh in on what kind of computing experience you have. For example, I would take a higher clocked Intel Core2Duo over a Quad-Core any day, simply because many applications cannot currently utilize more than two cores. The brand of your processor also can tell you alot about how it will perform. (celeron<centrino<pentium<dual core<core2duo<i5<i7 etc).
RAM definitely has a large effect on overall performance, I have 4GB in my MBP. Vista was just a terrible operating system because among other reasons it needed very powerful hardware to run smoothly at all. Windows 7 is running just fine on a dinosaur of a machine here (Pentium 4, 2.6GHz, (single core), 1GB ram.)
A faster hard drive is going to make everything snappier.
A lighter operating system (like Ubuntu) or even lighter applications is/are going to make even the meekest hardware run much much better.
Maxing out your RAM is definately a good idea, it is the cheapest way to make sure you’re getting the most out of all your hardware. All I’m saying is that RAM isn’t the only thing that matters.
cheers