These are a developer thoughts on iAd, if anyone is interested
I think that developers should not use ads in paid apps. Even 0.99$ apps. If one want to make more cash it should change the price. As as user, I will be really upset to find ads in paid apps.
I created a lite version of my contact manager ABContacts, and I added iAd. The app is still usable, the ad appears and disappears and when there's no ad, the screen is fully filled by the app information.
I've developed this simple contact manager app, that can create groups on the address book (no Exchange/Google), can send email and texts to groups, can show quick contact information.
The app CAN be useful to many, a lot of users simply don't need all the complex features the "full" version has.
Then I had to decide if release it for free, hoping that many user would buy the full version, release it at 0.99$, or give ads a try.
Releasing for free without ads was not an option because the app is not "limited", for example it doesn't limit to 10 people per email or something like that, it's simply doesn't have the full feature set of the "full" version. Since I have to use money to live

, totally free was not an option.
So I'm happy that Apple has introduced iAds as it simplifies the work for us developers to create useful apps that are free and I hope that other developers will use it wisely.
For who wants to give the app a try, here's the
macrumors thread where I've announced it.
P.S.
Do you know that ads are served on US only ? The rest of the world is not served by ads at the moment. This means that free apps with iAd around the world except US are now simply free, not free with ads

My app above is available only on US AppStore

; and since I live in Italy, I never saw a real banner on my app. If anyone can send me or post here a screenshot of a banner on my app I'll appreciate it.