I am a little more old school so I have never run a synthetic unless called for by the manufacturer. I also don't change my oil every 3K either.
Jeff
Edit: I have my reasons, mainly because I have watched cheap brands bottled at the same time as higher end brands without changing the actual product (just the bottle), but I have never had an engine related failure and have pulled down engines for performance heads, cams and things and have had engines with more than 150K with good crosshatching.