I have personally seen so many Sigmas lock up on people at the range that I wouldn't go near one. The Sigma was a hurriedly contrived response to the Glock. The trigger is about as good as a cheap staple gun.
The trigger can be improved, but I've also seen too many issues with the Sigma to feel confident in its reliability. I bought a NIB Sigma 9mm several years back and took it to the range only to find that the magazines would literally fall out of the magazine well about every second or third shot while being fired. Smith and Wesson said it was a faulty magazine catch, but replacing that didn't resolve the issue. My confidence in the pistol was poor enough at that point that my LGS took it back and allowed me to apply the purchase price toward a different handgun.