This is one I've been working on today and it took me a while to work out the dtrumming pattern. Weirdly, back in the day I probably played this rhythm with barely a thought to its intricacies, but the moment I started working on it with a strict, technical eye, I was all over the place for about an hour before I started getting a handle on it. I'm probably going to sit down with a metronome on a slow-ish 4/4 rhythm to get tighten it up, but also work on chord changes as well. As with anything, it's as much to do the time you put in to master it.