Does installing Xcode and it's mobile components slow down regular iTunes with iPhone syncing and performance? I haven't personally noticed any differences, but is there a toll on normal usage of iTunes and syncing it with your iPhone if you fit a developer profile by having Xcode on your system including relevant mobile components (Mobile Device Framework) that ask to be installed? I'm curious because during installation, iTunes is asked to be closed. I'm not part of the Developer Program yet and as such my phone is not yet marked as a development device.
I have been a developer for little over a year and had have not noticed any slowing down since and because of Xcode - the only thing is that sometimes making backups takes a long time, if you do not backup your iOS device everyday - but I don't see that being related to Xcode.