For those who play Alien Swarm frequently, I highly suggest you do the following. It won't make you Pro, but it will make your game more enjoyable and smoother.

Open notepad. Copy paste the following lines:

asw_realistic_death_chatter 1
asw_hear_from_marine 1
asw_marine_labels_cursor_maxdist 1000
mat_grain_scale_override 0
asw_fast_reload_under_marine 1
asw_camera_shake 0
bind . "cl_emote 6"
bind z "asw_suicide"

Change the bind X keys to whatever suits you best. Save it as "autoexec.cfg" in your Alien Swarm CFG folder (such as C:\Program Files\Steam\SteamApps\common\alien swarm\swarm\cfg). Next time you start up AS a couple of things will have changed, and your UI is more informative.

Secondly, download this file from SwarmArmory containing the torrent with the best maps of 2010:

http://swarmarmory.com/download-file?i=618&tt=1