I code in 2 differents computers with diferent username. XCode make a pbxuser file for each one, making necesary replicate the config from each one.
This is error prone, and the files are not diff-friendly so everything must be carefully checked. Any way to avoid this?
The info in the .pbxuser file is not particularly important - it's just personal settings like window locations, breakpoints, etc. All the important stuff is in project.pbxproj and this is the only file you need to sync/back up/check into source control/etc. You can ignore or even delete the other files in the .xcodeproj directory - they will get re-created with default settings.
the .pbxuser file does contain custom executables in there. So if you use a custom executable as a unit test runner, (or some other executable) you might have to share that file
When I have Xcode projects I might have to work on on multiple computers, I just have my project live on Dropbox. Then it's in the same folder on any computer I might use to work on it, and the changes get synced every time files are modified. That way I'm literally working on the exact same project on each computer.