will be fun or unfun on weekly basics _ all depends on rules set.
the thing that worries me is actually lack of entry fee _ if blizz wont make cash with this mode, whats gonna keep them on tinkering with cool rules sets for more than month?
I actually hope for entry payment as seen at arena - i dont care much about rewards now.
I am pretty happy that it is free. You might have enough Gold, but most People don't have it. Some can just Play one Arena round every two days or buying a pack every two days. For those it becomes too hard to enter. And when you are not interested in ranking then you don't have so many things which motivates you to Play. Furthermore, i think that this Play mode can incentive People to spend more Money, when it makes crappy Cards more attractive. The main reason i like to have a full collection is to have all Options when i Play PvE. Therefore i started to buy packs. If it would be just about ranking i wouldn't have done that, because i had already most of the good Cards and could Play almost every famous deck of the current meta.