Arduino at the moment doesn't support all the API present in wiring but we are adding them real quick. Expect some new commands in release 2 which will come out before the madrid workshop.
we have a page at http://arduino.berlios.de/index.php/Main/FeatureWishList
where you can see the current wish list and email up items you want to add to it
We created arduino to be opensource from the ground up, to be as cheap as possible and to be as democratic as possible. This obviously makes the board a little less powerful but we noticed that building your own board and being able to use the chip in a breadboard works very well with students.
The sintax is fairly simple and java-like to some extent. You should be able to pick it up quite quickly.
We are building a step by step guide but it will take a few weeks before it will be complete.
sorry for the confusing reply