Whether or not this idea turns out to be as fun as intended remains to be seen; however, I think that they are doing a good thing by trying something different to add some variety to the game. Maybe it will be popular, maybe it won't, at least they are trying to make ARR stand out and be a more enjoyable experience. They can always patch fishing to what we're all used to if this doesn't work out. I haven't seen any reason to believe that the ARR team is going to implement a fishing system that sucks, though.
I'm sure the system won't suck... but in any MMO (or any endeavor of any kind) the benefit must equal the cost. If we are to spend time doing something, there must be a reward. If the reward is "catching my biggest fish I've ever caught," I'd rather go down to the pond in real life... If it's getting new gear and other in game items, then sure it will be great.
That's a good point, and I completely agree with you. My in-game time is limited, and I like to use it making progress toward my game goals.