I agree with Abigail-II that consistency is important. Most editors handle 8-character tabs by default. Some of the worst indented code I've seen comes from folks that violate this (i.e. they write code with their editor to use 4-character tabs and your's displays the normal 8). If you stick with 8-character TABs, you don't really have to worry much about converting tabs to spaces to make things "more compatible" with other editors.

As far as indentation goes, I tend to use 4, but again use what will be consistent for the way you write code. For example, I've seen some people write code with multiple levels of indentation, but then stick with 8-character indentation and allow their lines to go past 80 columns -- absolutely hideous for someone to read.

bluto