I bought my 9VE mostly as a test case. I fully admit to having been a Sigma hater in the past due to bad experiences with the first generation Sigmas. People have been talking for the last couple years about how good the VE series is, so I had to give one a try. After the rebate I paid less than $275 OTD, not a lot to spend to give the pistol a spin.
I don't know if the one I got was just exceptional, but the trigger on it is nowhere near as bad as some folks have said. No, its not as smooth or light as a revolver, but the trigger pull is similar. Since I'm shooting mostly wheel guns right now, the Sigma fits right in. I dry fired it a bunch, which also helped the trigger, and in actual shooting it doesn't feel as stiff as it actually is.
All that said, I think the line was due for an update, and the SD series appears to be just that. I think the grip on the current VE is fantastic, and it looks that that is retained. If its true that it won't use VE magazines that is a real shame, especially since it has the same capacity. I would get one for sure if the mags would interchange. If not, I might just pick up a second 9VE while they are still available (if they do eventually go away) to keep around as a spare.
So far, just looking at the pictures, I say good job S&W. Now, where is the .45 ACP version? You will sell me one of those if it becomes available.
Overall, I like my M&Ps better than the 9VE, but it looks like the SD series has some of the best features of both.