I am interested in getting the iPhone app for this but I have a couple questions.

Does the app access my watch list? And also, I bid on a lot of the same/similar items...will that be a problem? If i have the iphone app does that give me access to the desktop app as well?Thanks

Yes, it can access and import your Watch List.

You can snipe as many items as you like.

I don't think you can install your iPhone app on your Desktop, so the iPhone app will not give you access to the desktop app.