I played with a pre-production prototype at the National Tactical Officers Association (NTOA) Conference last year at the S&W booth. It was prototype but the trigger was great, just like Steyr as the subframe is also steel. Short reset, crisp break - it felt like it would be a perfect alternative to Steyr as back then the service and support of our beloved guns was quite iffy.
The grip angle is exactly that of a 1911, and I don't think the bore axis is as low as a Steyr - I've still never seen anything that is lower. It seems to be between a Glock and a Steyr in that respect, so quite close. The slide is shorter (less tall) than the Glock so it is that much shorter. I posted about this a while back and Mr. Apathy replied that the M&P is an evolution of the Sigma and has the same bore axis but obviously everything else is considerably improved:
http://www.steyrclub.com/modules.php?name=Forums&file=viewtopic&t=1036&highlight=
The exchangeable backstraps have the biggest effect on the grip - much more than the Walter P99's.
Probably the biggest selling point to me is S&W behind it. Big company, big resources (they say it was developed from the ground up in the MA HQ for USA shooters) so aftermarket support with fiber-optic sights and trigger work should be very good. Only the 40's are out now and the 9's won't be out till later this year.
Charlie Petty is a friend of mine and he seemed to like it very much in his review for American Handgunner. And he shoots EVERYTHING - ALOT.
Jeff