The networkpx Project Blog has an interesting post on doing multi-row delete under SDK 3.0. It's a good post, even if they do credit the excellent Cocoa with Love blog for "introducing" a technique that I demonstrated three months earlier.
Anyway, the ability to do multi-row delete is now built-into UITableView starting with SDK 3.0, meaning you can now implement multi-row delete it with just few lines of code. Yay.
Or, perhaps not.
Unfortunately, using this functionality requires you to return an undocumented UITableViewCellEditingStyle value from tableView:editingStyleForRowAtIndexPath: in order to turn this feature on. To fully utilize the functionality, you have to use and override other undocumented, private methods.
Technically, doing that in an application submitted to the App Store violates your SDK agreement and is grounds for having your application rejected.
Will your apps be rejected if you do it? Who knows? Maybe yes, maybe no. It's even possible that people using the older, manual technique will get their apps rejected for using private methods even though that technique doesn't, similar to the Coverflow debacle from last year.
Now, I'm not going to advise you whether to use this functionality in your apps. It's a risk, and you have to decide how risk tolerant you are. I am going to advise that if you have any desire to use this functionality at all, go now and open a bug report with Apple requesting that they make the multi-row delete functionality available to developers.