I don't know, I feel like he's reaally culturally relavent, I mean he set up the ground work for people like Tucker Max and Chad Kultgen, although I feel as though he's able to explore the human condition a bit better. As for the shock value, thats the kind of thing that I really like, and Bukowski is a master at it. I haven't really read his poetry, but its pretty hard for me to find a poem I like so I can't gaurentee I'll be into it. Plus the fact that he's only able to write while drunk, and he always woke up in the morning not knowing how much he had written the night before just makes him badass.
I really love Bukowski, but honestly all the reasons you're mentioning are the reasons that I think he's given a bad name in the literary community. I don't think that he wrote with the intent of shock value, as that would likely entail that he was doing so merely to boost book sales (he wrote for many many years without even being published). Most of what seems like "shock value" is just him being honest; he wasn't a classy bloke, he wasn't sophisticated. He drank and fucked and slept on park benches.
But this is where I think some of Bukowski's best merits come from. For all the filth and obscenity that runs through his work, there is an inherent beauty behind it all, a simplistic, stained grace that transcends the dense indecipherable lines that have constituted much of poetry, both modern and in history. Bukowski was the first poet that I felt really spoke to me, that inspired me to express myself and to appreciate poetry as something more than a bunch of musty intellectuals jacking off to how great they are (which, admittedly, Bukowski did a bit of).
I don't guess I know how to explain it, exactly, but Bukowski really inspired something wonderful in me that I still carry on today. He changed the way I thought about life and art, and also is more or less responsible for me seeking out nearly all the other writers I now love.
Also, as a note: if you havent read Bukowski's poetry, you know nothing of his work. That is not to say that his prose isn't fantastic, it is, but I feel that to understand who Bukowski was you have to be exposed to his poetry. But give it a try, thinwhiteduke, you'll probably love it; as I mentioned, its not much like what is commonly thought of as "poetry", and has much of the same narrative structure as his prose.