One thing that would be nice is if you could right click and 'send to project' tabs from another project or an unclaimed window.

Or even have checkboxes by tabs in the project list that allow you to select lots and send them all to another project.

That way say you have a lot of tabs open and you suddenly realise that half are procrastination and half are part of a project, you could send the first half to a new project and keep the second half open as a procrastination window.

Adding to this the ability to merge projects would be cool.