Love the SD9. Excellent ergonomic grip, better trigger than the Sigma, closer to the M&P. Size of a Glock 19 with way better grip. Most accurate too. Has a front nite sight which works well for a nite stand gun.
They are a huge improvement over the Sigma. I'd still rather have the M&P though. While the trigger on the new SD-series is much improved it's still nowhere close to as good as the one on the M&P.