<p>I've used several apps now that launch the itunes store directly from the app. I'm even using some on my 2.1 iPod 2G.</p>

<p>I know there's a bug in 2.1 that prevents appstore links from working in safari, but somehow people are launching the appstore directly, not even through safari.</p>

<p>How do you do this? Is it an undocumented openURL feature?</p>

From iTunes, drag the icon of your app to the desktop, this will give you a link you can use directly (for example,
http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=284036524&mt=8
launches the AppStore to Crosswords, both on a desktop and an iPhone).
Pop this into an NSURL and call openURL on it.