Alex, I don't think that's true of the HTC Magic on Vodafone, if you read through the link I posted.
No a clue about the HTC Magic, but the G1 is definitely able to be tethered, because a friend does it with his laptop however he did say that it was a pointless endeavor without some sort of charge going into the laptop because the phone drains the battery (charging itself) through the USB ha ha..
I looked for Latitude too (after the upgrades) and did not find it, then I discovered there is an update to Maps available from Market that does seem to have it so perhaps this should have been part of 1.5 and got delayed.
Google Latitude, is bundled with maps, in Cupcake it replaces the "clear map" option, and becomes latitude, I've had a search or 2 on the market and no apps, theres a latitude enabler for Rooted phones but that needs the latest 1.5 update to run anyways, so that seems pretty pointless ha ha.. the WiFi router app is called "aNetShare" and requires root aswell