A friend of mine quipped a number of years ago that "the computer you really want always costs $5,000." Over time, the cost has come down, and you can certainly buy a high-end laptop for less than $2,000 today. But the point of the joke is still true. Unless money is absolutely no issue for you, you will have to make same trade-offs such as:
Faster CPU or more RAM
Lighter weight or less expensive
Paying more for a brand name or less for an off-brand product
Bigger and better display or less cost
You shouldn't ever judge a CPU just on the basis of its speed. Many facets of the architecture of a CPU besides its raw speed can affect its performance. For example, a Pentium M (Centrino) running at about 1.5 GHz performs on par with a Pentium 4 running in the mid-2GHz range.
For the most part, these choices will depend on your wallet. But a mobile laptop is a specialized computer, and some of the trade-offs really depend on how you will use the system. For me, it is extremely important to have a lightweight, small machine, but I also wanted a reasonable size keyboard. I chose an IBM model accordingly, and it has worked well on the road for me, and as a Wi-Fi machine but there were trade-offs involved. For one thing, my IBM machine doesn't have a CD-ROM drive on board. If I want to read a CD, I have to connect an external drive via a USB port. (But I can leave it behind on road trips if I don't think I'm going to need it.)
I purchased my IBM laptop a number of years ago, so the trade-off I made regarding my CD-ROM drive is by way of example. Almost any laptop purchased today will have a built-in DVD/CD drive.
The general bottom line is: do an assessment of what really matters to you, and purchase accordingly (see the sidebar "What Really Matters" for more tips on this topic).
WHAT'S REALLY IMPORTANT
As I've noted, you'll have to make the final decision on what's really important to you in a Wi-Fi laptop. To get another viewpoint on how to make this decision, I asked a friend of mine who is an expert consultant and has advised thousands of computer purchasers for her words of wisdom. Here's what the expert says:
Buy a well-known name brand, such as Apple, Dell, or IBM.
Don't be too cheap. You can expect a good piece of equipment to last a long time, so buy one that is rugged and with enough power.
That said, you don't need the latest cutting-edge CPU.
You should buy one with a CPU designed for mobile computing.
If your mobile is too heavy to take with you, you'll end up leaving it at home. Pay special attention to weight.
Buy a system with at least 512MB of RAM (by the way, 256 MB is the minimum you can get on a Mac portable).
Get at least a 40GB hard drive.
Ergonomics are important. Buy a model with a screen you like to look at, and a keyboard and other input devices that are comfortable for you to use.
Forget about cute. This is a computer, not a fashion accessory. Don't buy a computer because you like its color or shape.