I have Plutio.

I've used Trello extensively, as well as Basecamp, lots of other systems.

Ora is probably the most polished I've seen, so far... Intuitive interface. Quick app. Lot's of customizable functionality.

I created 7 test projects, to get a feel for the different templates. To be honest, I'm not sure what advantage a scrum or agile project template gives over the usual KanBan one, but it's interesting.

If you want a reasonably simple system for helping streamline your projects and improve your productivity, then check this out.

Cheers,
Wynne