The 2 stars is based on my experience, the museum itself is pretty cool. Just don't buy into the 'guided' tour. If there was anything different from the unguided tour besides the blue wristband, I have no idea of what it was. My experience felt as if I had general admission, but had bad timing as a group of 20+ other people happened to showed up at the same time and overwhelmed the museum. The guide was soft-spoken and only the few people right next to him could hear what he was saying. The little I did hear was usually him just pointing to something in a display and describing what's there, as in, "there's so-and-so's guitar. Pretty cool", which is, of course on the label right next to it. No more depth of insight. There were a few people in the crowd that were clearly well steeped in the culture and spoke a lot of their personal experiences, generally with certain bands, people and/or venues. Whis is all great, considering that's 'kind of' the stuff we were there to see. Except it was usually so obscure that it was basically irrelevant from my perspective.
In short, it felt like less of a guided tour, and more like having a unguided visit overrun by a flash crowd, with a few guys having a meet and greet with El Hefe, and if we tried to, we could overhear some of their personal discussions. I honestly can't think of any part of my experience would have been any different than if I'd paid general admission. Besides the blue wristband, and perhaps I could have had a more relaxing stroll through the place.
Again, the museum itself is worth a look-see. Although, I was surprised that I didn't see any particular display (or even mention for that matter) for either the Sex Pistols or the Dead Kennedys, who to me are arguably the most well known iconic punk bands of their era. Yes, I know it would seem to patronize the punk wannabes for whom those bands are all they know of the punk scene, but there is a reason that they are iconic. Maybe, even at $100 a head, they couldn't afford any memorabilia for those bands. At the "The Clash" display, there was one nugget of insider "guided tour only" detail: that display was, by far, the most expensive thing in the museum, and they even have cameras dedicated to it, despite the display being entirely encased with thick Plexiglas. So I suppose they blew their wad on "The Clash", which I wouldn't argue was a bad choice.
Bottom line, pay the $39 ($20 for locals), and check out some punk rock history. Don't get suckered into the $100 (no local discount) for the guided tour, which really just means 20+ other people wandering in at the same time as you.