Oh, not as queer as you'd think, but I'm not downloading things all the time, so Steam is happy to run in the background while I surf Subsim or do whatever. The only time it causes a hinderance is if it suddenly decides to download an update whilst I'm playing a multiplayer game, although it's smart enough to know that if you're playing a Steam game it won't download updates, but if it's a non-Steam game you're playing it doesn't know, so sometimes the best bet is to kill it temporarily.
Now unless you're on dial up, surely text based websites would not run that much slower with a Steam download running in the background? Videos, sure I can understand that, had that problem myself too, but text takes only a microscopic amount of data in comparison.
I can understand the downloading hell, but I've never had that problem with Steam...plenty of times I've had it with the likes of Internet Explorer, Getright, and that back in the 56k days, but the only time Steam has broken things it has been the developers mistake, not the service.
And besides, not much can beat spending an entire week downloading one episode of an anime, only to find that you've downloaded the episode with Spanish subtitles instead of English...
Not sure what's up with the Steam servers on your end, you might want to consider changing the server you connect to, some can be a bit funny, or Steam can have a brainstorm and decide to connect you to some obscure network. IIRC I was connected to the Paris network originally, but considering I live right on the East Coast I suppose I can forgive it, once I changed it to London the download rate was better.
Honestly though, I used to have a similar viewpoint to you, especially when Steam first came out and most people were still on dial-up, I figured that the whole idea was stupid and would never catch on. TBH I still have my doubts about the whole death of the second-hand games market via Steam, and I see that I'm not the only one if the current legal case in Australia is anything to go by. However, in terms of service, it has proven to be a fairly stable platform, the odd disconnect happens from time to time but it rarely lasts longer than a minute and unless you happen to be talking to someone over Steam at the time you don't even notice it.
Sure, it's not perfect, nothing is, but it's likely a more reliable download service than the DCS updater, and at least you can pause a download and continue later IIRC. I don't think you can do that with the DCS updater.
The biggest downside to DCS on Steam is that I'm not sure all the stuff is on there, and I've had a lot of problems getting my update version of Black Shark 2 to run on Steam, it'll take the full version of BS2 just fine, but the cheaper update option it does not like, but I think that is something that is being worked on by ED, again, it's not Steams fault, it's EDs fault.