From the b4 release notes:
Navigation -> Go to Header/Source now also work for non-project windows (although the plan is to remove the non-project windows).
I'm understanding this to mean that in future it will be necessary to create a project for everything. Is that right?
If so, the input I'd offer is that this is how Dreamweaver worked for years. You had to define a 'site' before you could make even the smallest edit to a file. It was a PITA and eventually Macromedia agreed to change the behavior.
TextMate has scratch projects though, which I hope would avoid the situation whereby the user needs to jump through hoops just to make a small edit to a file they don't usually work with.
drew.