[ziel]

I'm in the category you're describing. (Switched from Jira/Greenhopper to Pivotal and happy about it).

I think the divisive bit may, in part, be that Pivotal is a strongly opinionated tool while Jira is a fairly customizable and open ended tool.

For projects & teams committed to the process Pivotal champions, it's highly optimized. For teams using a different process, or who need to customize views for different people etc, Jira can provide more options, and be a better fit.

For me personally... at the moment, I really appreciate Pivotal's relative simplicity and the way it encourages folks to focus on the somewhat nearer term.