The app is basically a poor rip-off, so I don't think they're going to get any of my users. However, since the "Appname" vs "Appname Pro" is pretty common on the App Store I fear a lot of users might end up buying their app thinking that it's an ad-free version of my app.

The app developers have like 20 apps named "<something> Jokes" and from their blog (they have all their apps and submissions listed) I can see they've submitted a lot of apps ripping off other's names. They even got the nerve to submit an app named "FaceBook for iPad". I think this proves that this is not just an unfortunate coincidence and they won't be willing to remove the app if I ask them directly.

Has any of you dealt with this situation before? Since I'm not in the US, getting some proper legal advice regarding US law with these issues is going to be very difficult, so any advice is very appreciated.