Changing from tabs to spaces or the reverse can be a lot of fun with merges if your preferred diff program doesn't properly ignore whitespace/line endings.
http://www.hanselman.com/blog/YoureJ...InTheWall.aspx
The best standards are simple and lightweight, otherwise people just won't follow them, even at a professional job. Most of the ones I've written are 10 or fewer bullet points and all of the formatting issues are things that you can easily do with astyle or another formatting utility so that even if people prefer to work a different way they can easily make their code conformant before they check it in.
My personal preference has always been to use 4 spaces for an indent, but I'm fine with tabs too. In fact, tabs might be better for those mildly insane individuals that like 2 character indents, or the ones that were dropped on their heads repeatedly as children that use proportional fonts.