My wife insisted on an automatic car because she doesn't drive much and wanted to keep it simple. I was a bit hesitant, because when I first got my driver's license I really liked driving my parent's manual car. Now I've really come to enjoy driving an automatic. The two main benefits are when I drive in heavy traffic and either have to switch lanes or when I'm in a slow moving queue; in both situations there's one less thing to think about. I'm sure it makes it easier for me to focus on the surrounding traffic because there's less stuff on my mind.

Other benefits, when I think about it, are that an automatic frees up one foot and one hand. I can drive with my cup of tea or coffee without having to shift, which is great. I don't know if it directly helps with awareness, but it helps me stay awake.

This is the kind of thing I was talking about elsewhere. You need to take responsibility for maintaining mental engagement regardless of the transmission. Using a manual transmission as a crutch for mental focus is a terrible idea.