I'm pretty tickled that Blizzard is putting a Fishing daily quest into the game. Fishing is pretty much the red-headed stepchild of the crafting world, so any love we get is good love. Clearly the folks who came up with the quests have some fondness for the profession, since they put some actual TLC into the quest design.
So far I've done four of the five quests that are supposed to be available. One sends you to Nagrand to catch the World's Largest Mudfish and another takes you to Zangarmarsh for some shrimpin'. My personal favorite is the Crocolisk quest that has you hunting the sewers of Stormwind or Orgrimmar for renegade baby crocs. The croc quest was also more difficult for me, it took over 40 casts to catch the little booger. Most of the quests I was able to do in less than 10 minutes, but occasionally I had one that took longer. From what I can tell they are all designed for open water fishing, it took me a few days to figure this out. It can be especially frustrating when you are on the mudfish or darter quest, so don't torture yourself by hunting for pool spawns because it doesn't appear to matter.
The rewards are typical for a daily quest, at least the rewards I've seen. I usually get 7 gold and some random fishy items. This can include Jaggal pearls, water motes, vendor trash and some of the new fishing lures they've added to the game. The lures are comparable to aquadynamic fish attractors, so that should be really handy to folks that can't make their own. I've gotten 5-6 lures in each goodie bag, more than enough to keep my supplies up. There may be some additional rare items that drop from this quest, I have yet to see any but Wowhead is listing a new pet as a possible reward (so far not corroborated by any other sites, so who knows how accurate this is). Either way, a fun addition and worth doing if you fish anyway :)