Well, it looks like threads here in the Prius forum don't generate much response... but here goes anyway

I am considering a Prius as my daughter's first car in the next year or so; is there a particular year that has worthwhile changes, improvements, upgrades etc. that I should be aware of?
Or are they all pretty similar and just go by price and mileage (and condition of course)?
In other words, I don't want to get her an '06 and then find out..."Oh, you should have gotten an '07 instead because..."
What is the "best" model year Prius?