Content... well, that's a stone that's hard to get away from. In an online site, you're used to filtering things you don't care about. That's why web sites use things like popups and animations, blinking monkeys and crap like that - they know people filter out irrelevant things, and they're trying to work around it the best they can.
In a print magazine, though, you only have so many pages, it's not hyperlinked, you don't really skip stuff without actually flipping pages, which doesn't quite count. So the beginner articles that you'd not even notice on an online site gets thrown front and center in print.
So a lot of the complaints are based on the actual media itself, the nature of print. So why is it necessary at all?
Well... tangibility. Blogs have shown us that any fool can be "published" in an ephemeral environment, and blogs have also proven to us that many fools will be published - and there's very little available to distinguish the rubbish from the worthwhile, outside of experience. (I guess being crosslinked to from other blogs helps, but in that case, I'm completely irrelevant myself, which isn't pleasant to think about, so I'll ignore it altogether. I'm the most relevant person I know! :)
But print... print lasts forever. Print is something you hold in your hand, and show the relatives. When the internet has been replaced by silicon in our heads, people will think of the Web as being archaic and outmoded, and the association won't be as neat or positive... but print lasts forever as a record. Alien civilizations will find print before digital media, and use it as context to understand digital media.
That still doesn't say why JAVA needs a print magazine. Well... a movement needs a face. For the most part, Java is an idea, an intangible one (and one often misunderstood, from my vantage point.) Linux is the same sort of idea, but Linux has always had a "live free or die" mantra that inculcates a sense of community from the start, whereas Java is sort of a powerful, chained beast - and we resent chains, and Java suffers from that.
So a print magazine, especially an independent one, matters because it assigns a face to the concept of Java. In many was, the rebranding of JDJ was a master stroke, since Sun controls "Java" as a name and being "Java Developer's Journal" tends to carry a certain attachment that isn't always desirable... but a print magazine is still a living, breathing, tangible element you can carry about offline.
Plus, from what I've seen, most people don't read the online stuff as voraciously as I or Kirk or (probably) you do - most people view online resources as rare elements to look stuff up. They don't really SEE the community effort - they only see the results of the community effort, which doesn't help the effort grow and breathe.
So that's why I worked as hard as I could on JDJ - because I felt that we needed a print magazine, and still do.