Is this a question or a statement? Any performance degradation (very little) is well worth the safety you get by putting another copy of your control file on another physical disk.
I've never heard of any performance degradation due to control files. The only thing that comes to my mind that would cause any degradation (if any) would be if you're using RMAN and storing RMAN's repository information in the control files. And, the only thing about that is your control files will get bigger.

Now mirroring Redo logs on a SAN enviornment now that's a different story. let the games begin.