LOL, i use a TXT file on Dropbox!
Sometimes i see it's difficult to search within a lot of decks, and sometimes i forget what a deck did or other detail.
Text files are really essential, and your idea about using a google doc is not bad. Until now, i haven't used google docs for decks because i found it slower than a txt file. But... who knows, if i knew how to implement some things, i would use it for sure.
For example, i'd like to have a drop down menu from where i could select the marks and an auto-counter that shows me how many cards there are in a deck.
I really like that everything (in google docs) is in one row, it really improves readability.