Actually you are still rate limited when using OAuth credentials, it's just a higher rate.
If you can get users to log-in to your app and can then call the API with many different credentials it does help a lot tho.
I did a twitter hack at a recent hackday, and had massive problems with this. :-) http://jarofgreen.co.uk/2012/04/flocklight/ (It's Open Source if anyone wants to help)