All the ordinary keys will work, but you will find the function keys along the top row may not work. So where you expect to say, adjust the brightness on the old keyboard, will not be so on the new one. I can't give you an accurate distinction, as I don't have the old and the new side by side to compare, but that's the main difference. There may be some things you have to do on the Desktop where previously you could make use of a function key for the same thing with the old keyboard.
This does not make sense to me
Nor me... function keys shouldn't require rocket science!
I think Spark cured this for another person and the same problem...
PS. Apple is getting sillier by the day.