So, I think my HMC-150 has a problem with a soft focus. At first I thought I just wasn't being careful, but I just did two interviews where I was very careful, using the focus assist to help me, and the focus is soft.
It's entirely possible the problem is still a combination of me and the viewfinder. I'd spend the money for a better viewfinder, but I'm not sure that's the problem.
If I suspected it might be mechanical, what are the steps, in order, I should take to investigate the problem?
Try hooking up a nice big HD monitor to it and see for sure. Record what you see then play it back. If it looks soft then you have a camera problem. If not see your eye doc for a shiny new pair of glasses. :)