I had an M3 Manual and changed it for an M3 SMG after 8 months...loved (and still do love) the SMG. So flexible and simple to use when you get used to using it. It takes perhaps 2 weeks to know which setting you prefer depending on your mood at the time.
Seen many reviews of the SMG from journalists who seem to slate it but until you've driven it for a couple of weeks, you really can't appreciate it

Just my thoughts