Sorry if this has come up before and sorry if I'm missing something obvious...
I like to work with tab stops set to 4 characters and use spaces rather than hard tabs for indentation - otherwise everything gets messy when you process your file with something that expects 8 column tabs.
Something seems a little counter-intuitive with the soft tabs setting in TM. With Soft Tabs (Spaces) selected hitting tab still inserts a hard tab character. Additionally with Soft Tabs selected Text > Convert > Tabs to Spaces doesn't seem to do anything - it certainly leaves plenty of tabs in the files. With Soft Tabs turned off I still get hard tabs when I hit the tab key - but at least Tabs to Spaces works.
This is in Perl mode - I haven't tried other modes yet but shall if it's likely to make a difference.
So - what's the blindingly obvious solution I've missed? :)