There is no con's for bike lane!
Really I mean it. Do you have discussion of pro's and con's for sidewalk (aka pedestrian lanes)? No! Why? Because of course it is useful! We have to protect the fragile against the one ton metal box that is propelled at 50km/h!
However, there are many con's for how local politics have decided to implements bike lane because they fail the purpose of it: they are inconsistencies, not enough separated from the road, placed dangerously, etc. Each time we witness such mistakes which should contact our local council and tell them. OK, I agree, it's not always useful, where I live they don't listen at all. But that's why there is elections, and I vote where my mouth is!