It's been very smooth for us. We use UIImage+PDF to load and cache assets. The only issue is that you can't use PDFs directly in Xibs or Storyboards — you'll have to load them in code.

I'd recommend creating all your assets on non-retina sized artboards in Illustrator. We wrote a simple script to export all artboards to separate PDFs, using the name of the artboard as the file name.