I used TextWrangler for years in high school. It was better than Eclipse for quick and light needs when I was programming in Java. Earlier this year, I decided to stop using the tab key and replace them with spaces.
TextWrangler is setup by default to use tabs. Overriding is a little obscure. Go to
TextWrangler > Preferences > Editor Defaults. Once there, tick the Auto-expand tabs checkbox and you can specify the number of spaces per tab-key in the Default font selector below.