It's been a long time since I checked out Pivotal so I don't feel that confident in giving too much of an opinion.

However my main gripe with Pivotal was always two things: 1) Strict adherence to a Scrum methodology (forcing me to use a certain set of columns, etc) and 2) The UI. It frankly drove me nuts. The small text fields, small text areas and lack of wiki-style formatting. Anything longer than a few words was impossible to grok.

We flirted with trying it out about the time we adopted Trello but enough people had bad past experiences, like mine, that we never gave it a try.