Personally, I like it. People complain about the UI, but there's really only three locations I use, The friends window, the store page, and the library window. I see nothing wrong with any of these three windows. For those complaining that it takes a long time to do anything, I advise to check your system, as next to everything is done fairly quickly for me.
I like steam. I can legally purchase any game I want and have it all managed digitally. I don't need to go online to find obscure games on websites, I don't need a 2nd or 3rd bookcase to manage all my hard-copies, and Steam can manage their mods, Steam is able to include everything. We're not dealing with Origin, which only has a handful of publishers on it, we're talking Steam, who has just about everyone who matters. (I don't buy EA games, I don't like that company. I'm probably the only person left sticking to that boycott, instead of just saying I'll do it, and buying the first thing that pops up.)
Did I mention the mod support? Without Steam, I wouldn't have seen a large number of amazing games, and I wouldn't have seen them grow from nothing. To someone who finds the development of these things as a hobby, that's amazing.
The DRM is not intrusive, but for those who look, can be very easily removed. The Steam Overlay is very friendly in allowing me to quickly and easily join the servers my friends are playing. Steam helps me maintain a sense of community, as I play games with friends. The overlay allows me to not alt-tab the game and join the discussion, which is also placed on my 2nd monitor. While I'm not big on how it's going the way of facebook, at least Steam doesn't ask for any real information.
It, however, is a big problem for those who are unable to get a stable internet connection. And yes, I'm aware, on the west side of the world, stable internet is a luxury. It can be intrusive for those sorts of people. I can't find a solution for that.
The Tech support has been very helpful to me. I've got about 6 tickets revolving around Steam and the Source engine. All of which have either been followed up with a "I think you mean this, but tell me if I'm wrong" or a quick, clear and concise answer. I advised to go to the publishers if you're having issues with a game not made by Valve. What's Valve going to do about it, if you're having troubles with Assassin's Creed? THINK!
Valve is a company. And we live in a capitalist society. They're here to make money, not be your friend. Get over this hurdle, and realize that they've got a pretty good system.
There are some problems with it, I'll agree, but Steam has merely adapted other things that other companies have done. For example, the EULA. I don't agree that this makes it right, but again, it's the sue-happy society we're in, and they're merely protecting themselves.
People rip on the Half-Life series, and the "Trilogy Fear." Really, we're still interested in Half-life? Left 4 Dead's still fun for a little bit of lan-tertainment. I wouldn't want another installment of Team Fortress, and as far as I'm concerned, Portal's done. This really just ties into fans being foaming-at-the-fucking-mouth rabid. It's done. The series are no more. Valve's trolling you because the rest of the mentally developed world thinks it's hilarious.
That's what I'm thinking, anyway.