I do enjoy a sugar free treat, but be careful as they can not become your crutch. These should be used on an occassion not everday. These are still a processed food with ingredients that you should not be consuming too much of, like sweetners.
Sweetners can make your weight loss stall or even gain.
I am not sure what the effects on your gastro tract is as too much candy creates a laxative effect and laxatives when not needed can damage your body. I read before that people who abuse laxatives, their body becomes accustomed to needing them in order to poop. So if you consume too much sugar free candy I think the same could happen. Abuse when thinking of Sugar free candy may sound harsh, but there is a reality. How much eating of sugar free candy is considered abusing it, in reality we do not need sugar free candy. Plus you will need ointment for that inflamed sphinter.
So if you eat sugar free, do so in rare moderation.