It looks like most of the quests and mission are either soloable or are for small parties, so I doubt much of that stuff will be as time consuming as FF11.
Much of what was a time sink in 11 was having to get a party together, of course end game is something completely different, but WoW can be quite a time sink in that respect aswell.
I just hope end game content will be based around hard Faction leves, suceed and you get a piece of new shiny gear, I can see eventually guild marks being used to buy new weapons/armour.
Anyways, the retail game is 22GB after it's installed (how big it is compressed on the discs is still unknown), the relatively content-free OB was only a 5GB download.
Thats kind of interesting, The beta installed was just under 10 GB's for me, but still that 12 GB's extra we are getting in retail, that alone gives me something to smile about.