Update September 28, 2012: problem fixed, popover window stays open as it should.
You can assign individual to-dos (tasks) to different people and also set a deadline for a to-do, so they will receive an email notification about it. And this blog post is exactly about usability of adding to-dos and assigning a person and a date to it.
While creating a to-do you describe it (e.g. “blog post about Basecamp usability”) and continue clicking on a grey rounded button on the left. You click on a name of person responsible. And woosh… Suddenly the whole popover window with an option to choose a person or a date dissapears. Then you need to click the button again and set the date finally this time.
Instead of the to-do adding process being simple it becomes complicated and wearing as it requires more clicks than necessary.
How to improve usability of this process?
Second option is to switch the positions of a calendar and a list of people, so you would click a date first and choose a person as a second step. Just after this click would the popover window close.
Update (4th of July) – response from the 37 Signals support:
I shared your post with the team. I definitely agree with you on this one — assigning to-do dates and responsible party is a real pain at the moment. It definitely needs fixing. We’re working on getting the post-launch bugs and pains worked out, and it’s something we’re wanting to add soon. I’m sorry I don’t have a timeframe for you right now, but please know it’s on our radar.