Synthetic is great, as long as you're not putting it into an old (more than 25K miles) engine, and you can justify the cost. People make the mistake of putting synthetic oil in an old engine, hoping it will fix things or make the engine run better. It won't. What it can do, because synthetic is so slippery, is squeeze it's way past worn engine parts that have been plugged with old, thick oil, resulting in perhaps major oil leaks where the old, thick oil once was.
I'm not saying synthetic isn't good to use; it is. I'm saying start using it only in newer cars. Don't put it into an old engine.