Almost all S&W semiautos have magazine disconnect safeties (I think all except their new 1911, which has a warning to that effect because people know to expect a mag disc safety on a S&W).
Since I posted this, I handleda couple of S&W relatively new M&P pistols, and read an article on them. It seems that S&W has eliminated the mag disc safety on the M&P line, and Gary James writes about them very positively in the April 2007issue of Guns and Ammo. He reviewed the 9mm compact version, but has shot several and also shared the experiences of others who are familiar with them.