We are gradually clicker training a retreive and present in the obedience classes we do.
I don't know how the process ends, but we have started by establishing a good solid hand target. With dumbbells we are now at the point where we can send the dog to "hold" the dumbbell, give a hand target, and click/treat only if they touch the hand target with the dumbbell still in their mouth.
We've also been working on the "right up between the legs" positioning in a similar way to how millrace described, except that we have not incorporated a retrieve into it - we are merely getting the dog to learn the position required (it's essentially a target exercise - each shoulder must be touching each inside leg to get the click/treat). We're a long way from putting it all together as, with this being for obedience competitions, absolute accuracy of positioning is the key, but it does show it's perfectly possible to train a good present even if your dog is used to only learning through treats....
(Not saying that everyone should train with treats, but just that for those who have built up a treat expectation in their training, it is still possible!!) The key to using treats in training is that, once the behaviour is learned, you set it up on a variable reward schedule - so they don't always get a treat, but sometimes get just praise, a play or occassionally a really really mega yummy treat...