They've been releasing remade L4D1 maps on L4D2, and more are on the way.
How about bug fixes that have been in the l4d series since day 1, especially l4d2.
death toll finale is broken, people just camp the water area
charger goes through survivors and does not hit them
exploits in dead center map 1
too many health kits in a lot of maps
And the list goes on and on.
A new counterstrike is coming out.
With valve time, your great-grand kids will have the new CS on their steam wish list.
As gorcorps points out, they are supporting their other franchises currently.
I dont know if you are keeping track, but 1 or 2 tf2 updates almost equals 6 months of l4d/l4d2 updates.
~~ EDIT ~~
This is from a thread in the steam forums I am keeping updated, its a list of the tf2 and l4d2 updates since February 2011. tf2 receives 2 - 3 times the updates that l4d2 does.
TF2 Updates:
http://store.steampowered.com/news/?feed=steam_updates&appids=440
September 20, 2011
September 16, 2011
September 15, 2011 - large update, lots of fixes
September 6, 2011
September 2, 2011
August 30, 2011
August 23, 2011 - this was a good sized update
August 18, 2011
August 9, 2011
August 3, 2011
August 2, 2011
July 29, 2011
July 28, 2011
July 27, 2011
July 26, 2011
July 22, 2011 - 2 updates were released on the 22nd.
July 22, 2011
July 20, 2011
July 18, 2011
July 7, 2011
July 5, 2011
July 1, 2011
June 28, 2011
June 27, 2011
June 23, 2011 - Uber Update
June 17, 2011
June 15, 2011
June 14, 2011
June 10, 2011
June 8, 2011
June 3, 2011
May 31, 2011
May 25, 2011
May 19, 2011
May 18, 2011
May 13, 2011
May 12, 2011
May 10, 2011
May 9, 2011
May 6, 2011
May 5, 2011
Apr 28, 2011
Apr 20, 2011
Apr 18, 2011
Apr 15, 2011
Apr 14, 2011 - this was a huge update
Apr 7, 2011
Apr 5, 2011
Mar 23, 2011
Mar 21, 2011
Mar 15, 2011
Mar 11, 2011
Mar 10, 2011
Mar 4, 2011
Mar 1, 2011
Feb 28, 2011
Feb 24, 2011
Left 4 Dead 2 Updates:
http://store.steampowered.com/news/?feed=steam_updates&appids=550
September 23, 2011
September 16, 2011
September 9, 2011
September 2, 2011
August 26, 2011
August 17, 2011
august 12, 2011 - blood harvest released
August 9, 2011
August 5, 2011 - 2 updates were released on the 5th
August 5, 2011
July 29, 2011 - 2 updates were released on the 29th
July 29, 2011
July 27, 2011
July 22, 2011 - dead air released
July 15, 2011
July 1, 2011
June 27, 2011
June 17, 2011
June 3, 2011
May 20, 2011
May 6, 2011
Apr 26, 2011
Apr 22, 2011
Apr 8, 2011
Mar 24, 2011
Mar 22, 2011
Mar 10, 2011
Feb 25, 2011
Feb 23, 2011