The Sigma is well worth what is paid for it. I've owned a 40 and shot a few 9mm's and all worked as well or better than expected. The triggers are pretty rough but it's workable with a little time and maybe a striker spring replacement.
So far everyone I've seen was spot on POA at 25 yards. I know a few pistols that cost a good but more that have a problem saying that. for 300.00 or less you can't ask for more than that.
Bare in mind that it is not a target weapon and it never will be. It was built as a combat weapon and is a little loose like pistols of this type tend to be. Buy you do your part it will do it's.