Steam only bogs down your computer if it's an old piece of crap. Its memory footprint is infinitesimal by modern standards and I've found that its downloads are faster than anything else I've ever downloaded from the Internet.
As it's been stated before, once you activate Skyrim you shouldn't need to have Steam installed if (for some insane reason) you don't want to use it. Not sure if they'd release patches separately or not. Personally I've never found Steam anything but convenient, useful, there when I need it and out of the way when I don't.
The computer is new, the internet is old, because we don't have choices were I live. So when ever I get a game that requires steam, then i'm like crap now I got to spend a couple days downloading before I can even play the game, OR MORE. I'm trying to move, but I just got off unemployment so I got to get a few paychecks saved up before I do. Anyways The best thing about steam that I've seen, is that if you have a computer die on you, you install steam, and bam you have all your games back, after re-downloading them. other wise piece of crap for me because of the internet situation.