I've used Mobil One in all my cars since it came out. I used it in my Mustang, and at 60,000 miles I pulled the engine to stroked it and do a bunch of performance mods. The cyl walls looked great, the bearings looked new, the engine was very very clean. And I didn't baby this engine to 60k. We're talking borderline abusive driving. It saw numerious trips to the track. It was redlined more than a few times on a daily basis. I did burnouts and doughnuts like I had endless amounts of money for tires. Needless to say I was really impressed when I tore the engine down.
A friend of mine had a late 80's Dakota with about 100k on the odo. I was using Mobil one in my Ranger at that time so he decided to try it too. Mistake. He developed a small leak after using it. He then went to Valvoline Semi-synthetic and the leak went away.
I think the only other synthetic I would consider is AmsOil.
http://www.bestsynthetic.com/comptest.shtml