I can't remember much of anything specific about the Bourne movies either, which frankly is a blessing, as I recall being very angry and disappointed about just how much they managed to bastardize the book trilogy. They took the story of the first book, moved it from the mid 70s to the 2000s, cut out plot points, rewrote huge swaths of other plot points, and somehow managed to extend the unrecognizable mass out to three separate movies, the latter two bearing the names of the second and third books despite having no connection to them at all.
If you haven't already seen the movie trilogy, skip it and read the books. You'll get a lot more entertainment out of it. If you HAVE seen the trilogy, go read the books anyway. They're much better, and much different, from the movies.
As for the Bourne Legacy, I wasn't really interested in seeing it, and judging from MovieBob's review, I'm not missing much.