Note: spoilers follow...
I'm not sure why I didn't buy in, but I feel that the shotgun start bears a large part of the responsibility. Dirt 'n' blood was flyin' before I could bat an eyelash, and the movie jumped back and forth over three years at least half a dozen times in the first half hour. It was just too much, and Inman (Jude Law) and Ada's relationship of few words made that love all the harder to establish, and then sustain, for two and a half hours. Yes, they addressed this when the two finally met again, but that didn't make it any easier to sit through. It's a sentiment Sidney Lumet has expressed: real life is often boring. A tale of true love, in the most literal sense, doesn't necessarily make for good entertainment.
Of course, my expectations were undoubtedly inflated by all the acclaim for the movie that I read; I keep coming back to my brother-in-law's school of thought: the less you know about a movie going in, the better.