In my opinion, it is very important to weigh out why you need a new computer, how long you expect it to last and what you feel you need to get out of the computer. When I switched from PC to Mac, I knew I wanted to switch, but I also wanted to make sure I didn't spend too much, in case for some reason I didn't like the Mac. So, I got the Mac mini to see how I would like it.
My wife and I like to go away for the weekend, once a month to every other month, and I need to be able to keep up with things while I am gone. Sometimes I have projects going on (it seems like I always do) that I need to put a couple of hours in while I am gone, or we like to have something to watch DVDs on. My wife likes to check her email and keep up with some things she is involved in. So, for us, a laptop really was something we wanted and needed, but I wanted to make sure I really liked the Mac, before I went ahead and got a Mac laptop.
Being convinced that I would never turn back to a PC, I thought about what I would need and what the computer would do for me. No matter what laptop I purchased, it would make money for me, by being a machine I can code on for my freelance work and some day job work. So, the laptop then became an investment in my productivity for my work. This then made me think about being able to increase the speed as time goes by, hence the room to add 3 gigs of memory. I often times program at night, so the keyboard that lights up was a great passive feature so that I wouldn't have to buy a USB light to plug into the laptop. We like to watch DVDs on occasions, so a decent graphics card would be great. Having a large harddrive is always important to me, because I like to replicate my desktop as much as possible. (same programs, etc)
The 2k hit to the pocketbook was actually hard to swallow when I paid for my machine. But, I have already made that up and then some by using it to do freelance work. So, my laptop has paid for itself and I can write it off as a tax deduction because I use it for work.
So, for me, I saw it as an investment that allowed me to work from anywhere, and also will be a machine I'll be happy with for years to come because I can upgrade the memory considerably. Perhaps my view point might be of help, if not, forget I said anything. 