I love the ability to manage all of my projects from a daily dashboard. Moving each item on my to do list from to do, to doing to done really satisfies me and helps keep me accountable to making small steps towards my big goals daily!
I actually took a course on how to use Trello to learn it's different abilities. I think Trello could improve on communicating more with customers as soon as they sign up or sign on members of their team.
The ideal customer for this product is anyone in the field of project management - whether that looks like managing projects for your business or planning events. I also use Trello to keep track of personal to dos like sending emails or mailing out packages.
I absolutely absolutely love it.