Re: Issues I have with Steam.
Does the microphone Test work in tf2 Options? Note that if you use speakers (vs. headset) during the test you will likely get an echo, but do not worry about that. And you have to assign a key for push-to-talk (hold it while talking) in tf2 (I don't think the Steam default key "v" works unless you also assign that in tf2). But in an actual game, you will not hear yourself (so no echo) and you do not see your name, the only indication that "you" are speaking is an exclamation point [!] in a balloon at right edge of screen. So you will need to ask someone in game if they can hear you okay.
As far as mouse or other movement, "some" tf2 servers seem to lag (or maybe your internet connection to that server), which in some cases can result in stutter (ie, you keep jumping back to where you were a moment ago). Try reconnecting to see if you get a different server, or possibly a different type of tf2 game [like capturing point(s) instead of pushing the bomb] if you end up on the same server. With the Servers button you can look at History and if you right click on a server that is giving you trouble, you can blacklist it.
I have been running Steam and tf2 since late January, but in 64-bit Ubuntu 12.04. I also recently ran them in Win7 for awhile when my hard drive was failing (the tail end with Linux), and just installing Steam allowed me to install tf2 and all my items and stats appeared automatically (status is kept on Steam Cloud). Although, I have now installed Ubuntu 12.04.2 and copied my home dir to a new drive, so I am back running in Linux.
i5 650 3.2 GHz, 8 GB, nvidia GTX 750 Ti, 32" 1080p | i7-4700MQ, 8 GB, Intel HD 4600/nvidia GTX 765M, 15.6" 1080p | etc.