If anyone can post a sizable production code base that uses tabs that DOESN'T look like shit with a different tab width, I'm certainly open to being proven wrong.
Here and there's the problem. Too many people with editors that go round replacing N spaces with tabs everywhere to have sane alignment in a code base with >1 developer...
I do it myself but it requires a bit of maintenance and I wouldn't trust teammates with it. There will always be some guys who don't understand the idea and mess everything up.
In a team environment, now, I wouldn't chose anything but 4 spaces. Speaking from experience.
- with anything but 2, 4 or 8 spaces, some guys with incorrectly set up editors will mess everything up.
- tabs don't work well for alignment, and as long as you allow the tab character, someone will make a mess.
- 2 spaces is not enough to properly distinguish between blocks.
- 8 spaces can look very nice if your code is very clean. It won't be the case of your project.
Notice there are a couple examples in that code where multiline method calls are meant to line up, and if tabs are not set to 8 they don't line up.