This is actually a pretty good documentary for a first-time filmmaker. I'm not a huge Spock fan, so I found a lot of the late-60s home-movies stuff a bit of a slog, but it actually does a great job covering all the different elements of Nimoy's career. It leans pretty hard on all the ST:TOS footage you'd expect, but it makes up for it by interviewing a wide swath of Nimoy's compatriots, from fellow Star Trek actors to writers (D.C. Fontana), directors (Nicholas Meyer & J.J. Abrams), and even astronomers (Amy Mainzer). They even throw 'Seinfeld's Jason Alexander into the mix for some reason.
Also worth mentioning; it's rather overpriced on iTunes. $14.99 here in Canada.
It's now available on Netflix so that's great. Saw it last night and loved it.