When I look at the feature comparison between TextWrangler, which is now freely available, and BBEdit, there's really only one feature I would miss: Shell Sheets. These Shell Sheets are absolutely brilliant - at least when you've worked on old Macs with MPW like I have and gotten used to the workflow. Basically like a shell window in Emacs, except the editor around it is usable.
Otherwise, the only other limitation worth mentioning is not being able to build TextFactories with TextWrangler (though you can run them), everything else I personally consider absolutely dispensable - especially all those HTML tools I've never really used.
It's great that BareBones is finally providing a noteworthy free version of their editor.