Standing about 15 feet to the right of the depository window (the actual spot is an exhibit area encased in glass, so you can't stand there) it's not a huge amount of distance from the window to the spot where JFK was hit (which is still marked by an 'X' on the street, and visible from the window). Consipiracy theorists make this out like it's a tough shot, but, based on my very average skill with a rifle, I'd guess that any fairly average shooter could hit a slowly moving target as big as a pie plate about half the time from this distance, even with a crummy Italian rifle.
What I found most striking about my visit was the experience of seeing the famous 'grassy knoll' area first-hand, the spot where many conspiracy theorists say a second gunman fired from. I stood at the spot behind the wooden fence on the 'grassy knoll.
What struck me was the very short distance from this spot to the cement bench at the memorial to my left where Zapruder and his secretary stood--it's a clear, unobstructed distance of no more than about 20 feet or even less. It would have been almost impossible for Zapruder or his secretary NOT to notice a gunman from this distance, much less hear the sound of a gunshot, perhaps even from a gun with a suppressor. In fact, after I returned from my trip I did some Net research and found that Zapruder's secretary strongly insisted she neither heard nor saw a second gunman at this spot--having been there, I can now see why.
Not wanting to stir up the tin-foil crowd here, just wanting to share my impressions. To me, this was an example of where there's no substitute for 'being there.' And having visited the site, it seemed very plausible to me that Oswald acted alone, and could have readily made that shot. Even if he was as poor a shooter as is claimed, he only had to get 'lucky' once.
I'd be interested in hearing the impressions from others here who have been to the site. Did your visit make some of the alternative theories seem far less plausible as it did with me? Do you agree or disagree with the observations I made about my visit there?