I think the key to not being bored by the coda is to focus on Paul's vocals, rather than the "na na na"s. When I first heard the song years ago, I scarcely noticed Paul screaming and howling his lungs out, and I actually used a sound editor to cut off the end. Then when I read the transcript on Steve's Beatles Page (a seemingly defunct site unfortunately, which copies an old version of the What Goes On? Anomalies into each song's page, including "Hey Jude"), I thought, "I have to hear this", and now I know it's NOT just a four minute plus string of "na na na na"s, which indeed would be boring to me. I found that once I read the transcript and could follow along with Paul's vocals, it became much more interesting. I suggest those who see the coda the way I used to, give reading the transcript and following along a try, and see if it doesn't seem so long and boring.