I was a Toshiba guy, then went thru a few Thinkpads, and I'm now the proud owner of a two week old Dell Latitude D600.
It's a nice combination of size and performance, and I like the pentium M (I can't speak to the rest of the centrino goodies--mine does not have the miniPCI wireless card, since the Cisco card I have works just fine, thanks). It is very quiet.
The cons: It seems rather flimsy, particularly compared to the IBMs (I firmly believe that I could have beat somebody to death with my thinkpad, then subsequently booted up and checked email). The "nubbin" (or "nipple, for QL) is positioned in an odd fashion in comparison to either Toshiba or IBMs "nubbin" and it has a horrid tendency to "drift" (and it's only two weeks old). It gets very, very warm when on battery as the fan in throttled back. Dell should give you an option to eliminate the touchpad if you are planning on using the nubbin or another external pointing device. The S-video output requires a goofy dell adapter. Dell has
still not shipped my friggen DVD/CD-RW drive although that has nothing to do with the notebook, per se.
It's nice, I guess, but for the money I would have preferred an IBM. Unfortunately, my @!%$$

& employer signed a sourcing contract with Dell, so I'm kind of stuck.
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Don't feed the trolls.