Source: I learned all about my terrible running form that kept sending me back to physical therapy by a doctor who actually bothered to look at me running and cared enough about the biomechanics to tell me what I was doing wrong.
Just like math and science (or arts or music) doesn't come naturally to everyone, the same is being connected with and in control of the muscles in your body. If you've spent the bulk of your adolescent and adult life in a chair (like I did), chances are your core muscles and stabilizers are weak and you won't be utilizing them correctly just by running more.
That said, absolutely: if you're at all overweight, you specifically need to account for that in your regimen, and train up to running with that load. If you don't, you won't be running for long — one way or another.
I was also never running for pace. I found a comfortable pace and incrementally increased my distance. YMMV.
Zola Budd was pretty fast with no shoes. http://www.garycohenrunning.com/images/ZolaBarefoot.jpg
People set world records without using shoes even. The Vibram is less strange and more a compromise between foot protection and flexibility. In other words: gloves aren't strange, mittens are.
The single most important thing I've done for my running, is run more and lose weight. This is a universal thing. Everyone who gets good gets good via more running and losing weight. Running more can be hard. If there is a shoe that helps you do it, go for it. But as pace increases sometimes a shoe as minimal as a vibram can be problematic. Its certainly isn't necessary for everybody. People set world records without ever using a strange shoe.