Previously I mentioned the Marvell Libertas 8335 wireless chipset. In researching further the Marvell chipsets, it turns out that some of the Marvell drivers (though not the 8335) even have problems with Windows Vista.
The Ubuntu Linux community seems to have some nice documentation on using the Marvell 8335 chipset (the Linux driver is called mrv8k), including specific instructions for the TRENDnet TEW-421PC. The blog My Favorite Ubuntu has some nice instructions specifically about using the PM150NXT08 Wireless Adapter by NEXXT with Ubuntu Edgy.
The One Laptop Per Child (OLPC) project stirred up some serious controversy when the project went with the Marvell Libertas chipset, resulting in a very unhappy letter from Theo deRaadt. The Jem Report has an article that explains most all sides fairly well. In short, using the Marvell chipset required signing of an NDA, which means that the information thus learned cannot be used by the open source community to build or enhance drivers for this chipset.
It turns out also that the drivers for (some?) Marvell products require the use of proprietary firmware; thus, even with an open source driver the system still requires proprietary products to operate.
However, in spite of the fact that Marvell is the bane of the open source platform, it turns out that it seems to be the darling of the commercial builders. When Netgear chose the Marvell platform, Marvell released a press release about the fact and generally seemed to strut shamelessly. The press release was widely reported; here is the report as seen in the EETimes.
The Linley Group (who?) went so far as to state (in 2006) that Marvell’s chipsets were the best 802.11g chipsets in the market. This, of course, comes from Marvell (as reported by the Wireless Broadband Exchange Magazine here). If you want to see more awards and press releases ad nauseum from Marvell, check out their web site.
My current recommendation about the Marvell chipsets and those products designed around them: avoid them and go with the (perhaps older) better supported chipsets from other companies.