I've been using Steam for a few years now but I can't say I find it that good, more or less for the following reasons:
1) I can't install games where I want.
Not sure exactly what you are wanting, but Steam can install games pretty much anywhere if you go into Steam Settings and configure the "where I want" in the appropriate place. You can have multiple "where I wants" in fact, and when you install a game with multiple "where I want"s configured, there is a drop down that lets you choose which "where I want" that you have preconfigured. That may or may not be what you want, but it is an option which you may or may not have been aware of.
2) For a storefront limited webbrowser it looks horrible.
Subjective assessment, I think it looks quite good personally. Neither of us is wrong.
3) Apart from enforcing DRM upon us it has absolutely no functionality I use which my operating system can't do.
The steam client doesn't enforce DRM, it's just a piece of software to access Steam services and manage your games. Individual games may or may not enforce DRM, and they may or may not use Steam's optional DRM service (Steamworks CEG), however that's linked into the game itself IIRC, and not the Steam client. There are lots of DRM-free games on Steam, and oddly enough some of them are actually the GOG versions of the games such as Tomb Raider 1-3 for example (complete with GOG's launcher).
5) It's mandatory for downloading every game and mandatory for playing almost every game. Good luck finding out which are and which aren't since Steam dumps everthing in the same location (see point 1).
Not perfect perhaps, but these links are helpful in determining that both before and after purchase: http://pcgamingwiki.com/wiki/The_Big_List_of_3rd_Party_DRM_on_Steam http://steam.wikia.com/wiki/List_of_DRM-free_games
Funny is that everybody is ranting on always online DRM but miraculously Steam gets away with it, granted it can be considered a Lite version of always online as it allows some layback, still I have been kicked out of games several times because it lost connection.
It's not only possible but actually very common for many things in life to use something and also dislike aspects of the same thing enough to complain about it because everything isn't without its flaws and we're sometimes willing to buy and use things that do have flaws because they still have value to us, but we will also potentially express our opinions about the aspects of the thing that we don't like as well. Pretty much everyone does that with things in life most likely including you, whether it is Steam, a refrigerator, or a corner store burrito.
Steam is rather convenient and has a lot of features that many people find useful, myself included. It also has it's own problems like just about everything in life. Everything has pros and cons pretty much, but they're also in the eye of the beholder and one persons +1 is another person's -1. I hate DRM, and I actively avoid the games on Steam that contain the types of DRM that I personally find very invasive and consumer non-friendly (Ubisoft and EA, I am looking at you...). I consult the URLs I shared above before I buy a game to ensure it is either DRM-free or that it has minimal DRM that wont harm my gaming experience likely in a way that is obstructive and thus I can find compromise with for the given price. I certainly respect those however that refuse to buy anything that contains any DRM whatsoever as that's also a valid and worthy personal choice too if it gives a better experience to someone.
For what it's worth I'd be rather upset if I got booted out of a game like you mention as well, which is why if someone does choose to use Steam it is very important to check the two DRM lists I posted above. It's up to game developers/publishers who sell their games on Steam whether their game uses any form of DRM or not, and whether it uses the optional Steamworks CEG DRM. In my opinion, if a game does use DRM, any anger over it is best directed at the publisher of the game and its developers however, and not at Steam because Valve does not require any games to use DRM at all. You do need to use the Steam client to download/install your games and some people consider that a form of DRM (although I don't because no "right" is being "managed" in the process), but then some people consider just about anything they don't like about a game or service to be "DRM". DRM has virtually become synonymous over time in gaming communities to mean "absolutely anything I don't like", kind of how just about any criminal activity these days is called an act of terrorism.
Anyhow, to be clear, I'm not defending Steam - just pointing out some information and some of my own personal thoughts about it as they apply to me and me alone, and respecting other people's views which may differ or even be the exact opposite of mine. I greatly prefer the GOG way of doing things and hope to see the entire catalogue of GOG-worthy games on Steam come to GOG some day, while the indie shovelware crap there stays there or goes to Desura. :)