My first child was never swaddled and she was a horrible sleeper =)
My second child I swaddled for 6 months and she was amazing. After I stopped swaddling she woke up 2-4 times a night. Why did I stop swaddling? Because she was moving around more in her sleep and I figured it was a natural transition for her as that's when they learn they have feet and hands and try to roll over =)
It wasn't an easy transition with either of them swaddling or no swaddling - I think sleep time is affected by way to many other things - teething, gas, being hot/cold, growth spurts, etc to be completed changed by whether or not you choose to swaddle.