Since we started with HubSpot, they have improved the UX and they made things more intuitive in their platform: they unearthed a lot of the features so that what was 5-6 clicks away is now only 1 or 2. With the CRM, it makes for a good all-in-one marketing suite.
Trello is intuitive and it is easy to invite people to it. You can also quickly move things between lists. One frustrating thing about Trello is that you can’t assign things to people--you can only mention someone in a comment area. You can develop a list for someone but you cannot track it.