I think one problem with this is that it doesn't behave like a set which I believe acts_as_taggable_on on does. It doesn't allow a user to tag an object with t

I think one problem with this is that it doesn't behave like a set which I believe acts_as_taggable_on on does. It doesn't allow a user to tag an object with the same tag more than once. It seems that the Postgres array method would (without other backend code to prevent it) immediately allow a user to tag with the same tag over and over. So for users who are more comfortable using an out of the box solution (even if they are using Postgres) they may have better luck with acts_as_taggable_on. Either way, this is pretty cool!