We have been using CodeIgniter with svn since last year and half.
Here are few things that we follow to avoid conflicts/unnecessary file commits. We add following files to ignore list:
user_guide // It is important that all the developers have this for quick reference but adding it to svn is pointless.
application/config/database.php // Instead commit database.sample.php as this file has db settings for a specific dev machine which might conflict.
application/cache // There is no point adding developers cached data to repository.
application/logs // There is no point adding developers logs data to repository.