I see the carbon tax as a 'stick' (to penalize undesired behaviour, in this case emitting carbon), but it needs to be coupled with a 'carrot' to encourage the desired behaviours.

I'd like to see a carbon tax coupled with massive investments to make public transit legitimately good. There are too many places where there is no viable alternative to driving, a carbon tax will unnecessarily punish those people without giving them a reasonable alternative.