I had the implant for a couple of years and had it taken out about a year ago to go back on the pill and my periods are still playing up. The nurse I see doesn't seem to think it is a major concern and keeps saying my body will settle down eventually.
I took up running last June and was a smoker until just over two weeks ago, averaging 10 a day generally.
I never really felt like it caused me any particular problems with my running, and I've not noticed a vast improvement since stopping, although admittedly it is still early days. The morning cough has gone but I do sometimes still get a tickly throat at the end of runs. I've never felt like my breathing has been particularly laboured.
I would always keep an eye out for other smokers at club/races but never saw a single one!