I've owned or been issued ten Sigmas, including an SW40F, 2-SW9F's, SW357V, SW40V, 2-SW40VE's, SW40G, SW9VE and SW9GVE. Out of all of them, and a combined round count of tens of thousands of rounds, mostly my cast bullet reloads, I've experienced one, yes only ONE failure. It was with my issued 1st Generation SW40F during qualification one time shooting factory Winchester ammo. It failed to fully extract the fired round from the chamber. Other than that, no malfunctions of any kind.
When the S&W Factory Store is running specials on Sigmas, you can buy a VE or GVE in your choice of 9mm or .40 for $279 plus 5% tax. Most shops sell them for between $289-$329. I saw one shop who had them priced at $349 and I laughed. I believe dealer price is around $239 on them. So, covering their overhead, insurance costs, etc, even at $329, it's a very fair price.
Last time I was at Kittery, which was about a year ago, I was surprised at the prices there. I hadn't been there since they renovated the gun area, but their prices seem to have gone up considerably since then. I didn't understand when I saw new Sigmas for around $329, and used ones a few cases over, same model, etc, for $20 more! No spare mags, holsters, nothing!
Anyway, there are some modifications you can do to the Sigma's trigger, but you are gambling with reliability when you do them. Some people have decent luck with using a reduced power striker spring from Wolf, others experience misfires. There is a trigger mod posted on the S&W Forum, but I HIGHLY recommend AGAINST it. You are reverse engineering it back to a 1st Generation gun which will probably, at some point, have problems. If you modify your Sigma in any way, never, EVER use it for CCW or home defense use. It's nothing but a range/plinking toy after that which you cannot trust to fire when you may depend on it.
If you want a polymer S&W with a better trigger, get a new M&P. If you want an economic S&W polymer pistol, get the Sigma, do a lot of dry fire practice at home, master the trigger, and find yourself more competant with any other handgun you pick up after that. It's happened over and over again. People get the Sigma with its heavy trigger pull, dry fire practice a LOT at home while concentrating the whole time on slow, steady trigger pulls keeping the sights aligned, and they find that they are better shots with ANY other handgun they pick up.
Let us know what you end up with.