It needs news that's actually reported while it's still relevant. I mean, we all knew the remasters of the older albums were coming out this year long before U2.com announced it.
Even more, though, it needs more exclusive content. I liked how they were doing that playlist series, but it's been updated only twice this year I think. They could have blogs, if not by the band themselves, then by crew members, as they did with Willie's tour diary (though I think they could choose someone more interesting--all of Willie's entries started sounding the same to me after awhile on the last tour). I really liked how they did the crew profiles, but those seem to have disappeared. I think it's embarrassing for U2.com that we have more "exclusive" content than they do, and we don't charge for our stories!
Aside from presale codes, I have no idea why anyone would want to join U2.com. The Zoo allows ridiculously huge signatures, which slows load times on pages and means few messages appear on one page, which means it takes forever to read a thread. Beyond that, the search feature is really clumsy; in fact, the whole interface is. I think this forum puts the Zoo to shame in terms of ease of use and functionality.