Intel's Pro/Wireless solutions that make up the 3-piece Centrino(tm) isn't very special at all. They will release an 802.11a compatible solution later this year, and you'll have to wait a long while until 2004 for the 802.11g solution.
There are better options available now. Broadcom mini-PCI cards currently support b/g or a/b/g, and are available in various guises, such as the Dell TrueMobile 1300 or 1400, respectively. In addition, the Broadcom solution offers much greater range than Intel's Pro/Wireless in 802.11b mode, not to mention the issues Intel is having with interoperability with various VPN concentrators/endpoints.
You lose the Centrino(tm) label by going non-Intel for the wireless solution, but current .11a/g options are much more attractive than Intel's own Pro/Wireless solution.