I have been using 3.0 since I got my macbook pro in 2007. 3.0 works fine. I did get 4.0, but will not install it. There are so many problems and unanswered queries, to me it is a waste of time and money to use 4.0. Does anybody have anything positive to say yet? Like 4.0 is TOTALLY faster than 3.0. Or 4.0 installed and EVERYThING works perfect. And if so on what mac device ?