Personally - I would avoid them. Their reliability has gotten much better from the days they first were released - but the trigger is so heavy - It isn't a good gun to have fun with at the range and see how well you can shoot.
Most sigma owners end up getting rid of the gun after they find out that there isn't a whole lot you can do to change the trigger pull - And, in all fairness, if they bought the gun that way, they should have known better.
At Handgun Forum, there are some happy Sigma owners. And, I suppose for a truck gun or a gun that you only occasionally use and you want a cheap gun - they might be ok.
For the same amt of money or close to it, I'd recommend a Stoeger Cougar - it is basically the same as a Beretta Cougar, but Beretta transferred the equipment to make the gun to a subsidiary.