I do have the bars on the side, and the image is somewhat fuzzier, but not much
I think it's a lot fuzzier, especially if you have a bigger monitor like I do (24 inches). Whereas photographs in the regular-size window make you want to scream, "Oh! How beautiful!", the same photographs in full-screen will probably only make you say, "Well, that's nice."
(That's still better, though, than a full-screen Tiger Woods game, where the typical reaction of a WGT HD-spoiled player might be head-shaking and, "Oh my, how pasteboard-like all this is!")
As to those hidden running processes, you're absolutely right. It really greatly depends on the quality of the player computer whether the meter stutters or not. The quality of a computer is perhaps more important than whether the computer is new or old, and what its exact tech specs are. I play on an almost 3-year-old notebook, but it was frighteningly expensive back in 2006, top of its class with an independent 256MB graphics card, and the quality still shows in 2009: I hardly ever see meter lags and stutters.
As to full-screen making it easier to hit the perfect shot, unlike you I believe that it really does that. However, it took some time getting used to (at least a few days) after transferring to full-screen play, until the advantage could be clearly felt. I wouldn't dream of going back to the regular-size game window today.