While majority of users still prefer the old fashioned OFP style command line driven mod handling, there is also another way of doing it, using the in game expansions manager and documents settings. One real advantage of doing it that way is that it no longer matter from where you launch the game (be it steam, other version etc.). It makes clean installations also much simpler than messing within the game folder.
Example how I use the system:
* create DayZ folder in C:\Users\maruk\Documents\ArmA 2
* create sub folder Addons there and download / extract files from http://www.armafiles.info/dayz/ to it
* run the game (I use the latest beta from http://www.arma2.com/beta-patch.php )
* in the game go to the Expansions, select DayZ and click on Enable button, restart the game
* now the mod is installed and I can play easily with it anytime (using beta, or normal steam version, or sprocket version)
For me personally it is simpler than toying with commandline options and interferring with game installation. I understand that everyone has different taste and that is why the original mod commandline is kept intact since 2002 I just thought some may simply not understand the more modern alternatives available now.