Glad you asked
I'm interested in this! What happened?
Here's the list. Many of these are small issues, but combined with the big problems I finally gave up.
Before I start, I was excited to get Steam as it opened access to many new games. I went into my Steam experience excited and hoping (expecting) it to work. I had a positive attitude going in to my Steam experience.
1. The Steam client UI is horrible.
2. You need a separate logon/password for user support.
3. I eventually created a separate email address to handle the traffic I had for the problems with Steam.
4. Here is the complete text of one of their replies: "Hello Patrick, Thank you for contacting Steam Support. What issue are you experiencing with your Steam account? Or did you just want to write in and complain?".
5. Clicking on a Steam-supplied link in any of their reply emails takes me to a screen that asks me to create a new Steam support ID. I already have a Steam support ID, and the link has a ticket number in it. How can Steam think I need a new support ID?
6. I realized I was spending a good percent of my game time supporting Steam problems, not, you know, playing games.
7. I had some problem downloading Portal 2, don't remember know what the deal was.
8. Many problems with Steam lead to a domino effect where solving one problem leads to another.
9. On April 21, 2011, I have 6 emails from Steam regarding changing my password. This is to my support account, and did nothing to respond to my problem with downloading Portal 2.
10. Had some issue with being double-charged or not getting my secret unlock key for Eve Online in mid-2010, don't remember now what the exact issue was. Took a long time to resolve.
11. They closed one of my tickets as resolved, then denied they do that.
12. I exchanged 22 emails with them June 17 - 21, 2010. Their replies were unhelpful as they did not resolve the situation.
13. Had a few crashes in mid-2010. This had not happened since.
14. Had a support request denied because the subject line was not long enough (although non-blank).
Boy, dredging up all of those dark memories has been therapeutic for me. I have decided that setting up a game portal (Steam) that must be used to access all of your Steam games creates a dependency on that portal. If there are any problems, all of your (Steam) games will suffer.
I have since moved into the light of the MAS. That is a portal, but only for discovering, acquiring, and updating games. Actually playing the games uses the normal process for running any application, which has (for me) been much more problem free than Steam.