I hope that this post will catch the eye of people BEFORE they buy their first Arduino, but it may be of interest to others too, especially if they are thinking of expanding their Arduino hardware.
First we had the choice: USB circuits on Arduino, or in cable?
Then came 3.3v or 5v?
And now, happily, there is another choice, if you don't "go with" having your USB components on your Arduino.
I speak of the components which allow you to plug the Arduino into a big computer, for receipt of the program generated for the Arduino in the big computer.
Details of these choices written up at...