Theo,
There are so many factors involved in WLAN connections, it is hard to say for sure just what, exactly, is a realistic speed.
LINUX is often faster than XP here, because LINUX has a more efficient cache algorhythm. Windows Vista Service Pack One, according to its fans, is also faster, also because of certain 64Kb limitations in the XP design.
My personal experience is that identical computers, running identical OSs can achieve significantly different through-put.
There is a serious bug in the software for many Aetheros WI-FI cards as well as some Netgear, causing these cards to run at a far slower speed than they are capable of. You can look this upon the internet and find solutions, should you have such a card. I had that problem with a Netgear a few years back. It should have run at a steady 56Kb, but never got over 12Kb, and that with dropouts. Turned out the software had instructed windows to throttle the card back to that setting by default. Since it was not to the 'b' standard, I didn't pick up on it.
All wireless cards will drop their speed back to the speed at which they have a stable connection - by their definition. Many networks, especially older ones, will drop all cards to the level of the slowest card. Sometimes, the router is set to the ancient 'b' standard and not to a faster one...and so on.
Hope that helps in your search.
):
