If I said that I was surprised at being considered "knowledgeable" about Marvel's history, that goes double for DC. I never even read DC Comics until I was in high school, having utterly rejected the output of the company as a child, based primarily on Superman #337, which made so little sense to my four-year-old self that I pretty much gave up on everything associated with the company. (If you don't know who Don-El and the Superman Emergency Squad are, the thing is sheerest gibberish.) It wasn't until my future brother-in-law told me that DC had really improved its output that I decided to take a flyer on their comics...and promptly ran headlong into 'Armageddon 2001', right after deciding that 'Hawk and Dove' was my new favourite comic. (DC Comics: Proudly crushing the dreams of its fanbase for over two decades.)
And yet, here I am, having read most of the Silver Age output of DC and a good chunk of the Bronze Age as well. What really surprised me about it? What do I want you to know? Well...
1) Some of their best material wasn't superhero stuff. Before Julius Schwartz kick-started the Silver Age by recreating most of their superhero properties with a sci-fi twist, DC was surviving the lull in interest in guys in funny outfits by publishing a wide variety of comics in a number of different genres. And even after the superhero genre took off, DC hedged their bets for several decades. They published war comics, westerns, horror and romance...and they produced a lot of brilliant, iconic material. House of Secrets and House of Mystery were both excellent, especially under Joe Orlando, and Joe Kubert's Sergeant Rock and Enemy Ace were both legitimate works of high art. Jonah Hex was such a brilliant, ahead-of-its-time western that it's a damn shame that it produced such a loud, stupid, anti-quality movie. And they even produced some good fantasy comics, like 'Warlord' and 'Amethyst', before it became apparent that the audience for comic books had diminished to superhero fans and nothing but. Changing audience tastes were as big a part of the problem for DC as anything else.
2) The Bronze Age was really rough on DC. One thing I've noticed about reading Marvel vs reading DC is that I look more and more forward to reading Marvel's books as they get into the Bronze Age (and even beyond, into the Eighties and Nineties)...but DC's superhero books got weaker and weaker as they went on. Part of it was the way they went deeper and deeper into their own over-complicated mythos; the aforementioned Superman #337, which involved a renegade member of the Superman Emergency Squad escaping Kandor and being attacked by a whole gaggle of supervillains who were all Superman in disguise, was a classic example. It also served as an example of the way that they got more and more obsessed with gimmick plots and bait-and-switch "twist endings"; every issue seemed to revolve around creating some impossible situation, then coming up with a contrived explanation for it all. (And all in twenty-two pages...DC took a long time to adapt to the concept of the "multi-parter", and it shows.) But mostly, and I think Chris Sims has also said this, DC was trying so hard to be Marvel that they forgot how to be DC. Marvel was "hip", it was "relevant", and it catered to teenagers and young adults...and so DC wrote all of their comics like they were going through a mid-life crisis, using the slang that all the teeners were into and chasing the hip trends. And there is nothing guaranteed to feel more awkward than watching someone in their forties try to act like a teenager. The Bronze Age was full of DC comics that were trying too hard, and it showed.
3) DC's second-tier heroes were second to nobody. That said, DC had some of the most fun back-ups and second-tier superhero titles in the business, especially in the early Silver Age. The Doom Patrol, the Metal Men, Metamorpho, the Elongated Man, Hawkman and Adam Strange were all great titles worth picking up and plowing through in a single sitting. Even supposedly ultra-lame characters like Aquaman had surprisingly great solo titles. They all floundered a bit in the Bronze Age, when DC wasn't sure what to do with themselves (actually, now that I think of it, Marvel floundered in the mid-Nineties the same way when faced with a challenge to their teen-cred from Image). But they had some great material in there.
4) DC did a better job of imitating Marvel when they used Marvel writers. Admittedly, there's not a lot of material from the Eighties in the 'Showcase Presents' series, primarily due to royalty issues, but the stuff they did put out shows that when Marvel writers crossed over to DC, they produced some fun material. Batman and the Outsiders, while not an instant classic, was a solid title with a lot of Eighties team book energy, while Booster Gold deserves a lot more credit than it got for trying something new and interesting with a character who wasn't your typical superhero. And although it doesn't have a black-and-white volume, the Teen Titans absolutely exploded in that era.
5) Comics in the Silver Age were freaking mental. Between the super-compressed storytelling that necessitated very sudden plot developments (one issue of Aquaman announced, in the span of one panel, that there was an ancient city filled with evil demons that only came into alignment with our universe once every thousand years, and this was one of those periods of alignment--this would have been about ten issues of foreshadowing and build-up in a modern comic, but Aquaman got it out of the way in less than half a page), the abrupt conclusions that returned everything to the status quo, and the assumption that they were writing for an audience of small children who accepted arbitrary rules to their stories much better than adults, DC wrote some of the craziest stuff you can imagine. Superdickery makes fun of it all, primarily because it does look pretty silly when you imagine it as part of the same line of comics that gave you 'Identity Crisis', 'The Dark Knight Returns' and 'Watchmen', but there's a certain perverse glory to it all if you just take it as an a priori assumption that it's not going to make a lick of sense and let it all flow over you. You really do have to read DC's Silver Age work differently than you do modern comics...most of the complaints from modern fans are from people who either can't or won't do exactly that.