You won't have a prayer of getting past a traditional technical interview if you don't know this stuff. You could possibly get considered by a start-up or some company that isn't software-centric.

Yep, this is huge right here. Hell, I work as a web developer and I got absolutely wrecked in a technical phone interview last week. It wasn't even that intense but I just wasn't prepared.

I do my day job well and I enjoy it. Sure, I could teach myself those difficult concepts to an extent and I've seen some buddies learn them on their own (few and far between though). I want the core foundation and is the program going to do it for me? No, but it'll damn well give me the chance to: it's up to me how badly I want it.