It has also fixed the 'files different from server' error some people that had downloaded the DLC (including myself) were having...this was happening when people that had not donwloaded the DLC were hosting games...apparently the DLC acted as an update too so people without it had different files from the ones with it. Had same issue with MW2.
i do not know much about the in-game updates, however what i know is that Activision hasnt fixed the main problem when looking for games....you still stuck with 2/3 games available when searching compares to 50 before the DLC! I have lost hope they will ever fix that one day!
If anybody knows a way of getting more games when searching, please shout!