I've been leveling up fishing lately (hit 373 last night, along with 375 cooking, thanks to El's great guide), and I've actually found it pretty fun. It's a little too boring to do it without something going on in the background (last night it was the Cubs game, as depressing as that was), but it's kind of fun just to throw a line into some random water or pool and see what comes out. That said, the rewards could use a little tuning -- while events like the STV Fishing Tourney are fun (I've done it twice now and haven't won it yet) and offer some nice items, fishing itself even at the highest levels just isn't as rewarding as, say, running dailies or Heroics. The only reason to run it all the way up is really just to say you did -- while there's a promise of a Mr. Pinchy somewhere out there, there's no real fishing endgame in the way that there is for the rest of the game.
Which makes Qann's suggestion intriguing -- he says that high level fishers should have access to certain areas via boat that offer them tougher fishing challenges, and better rewards for it. A boat could shuttle you out to a remote island or location, where only certain fish could be caught or found. And we don't even really need a boat -- just more events like the STV Extravaganza (where certain fish that appear in special pools can be turned in directly for items) would be great. And why is it that the best items obtained through fishing are apparently scrolls? Why can't we fish for Badges, or even have a fishmarket, where fish can be exchanged for gems, crafting materials or other rewards?
Even Blizzard admits that there's a lot of work to be done for fishing, but it doesn't seem too hard -- if they're giving out epics for holidays, fishermen and women who make it up to 375 should deserve some good loot for their hard work as well, whether it's through Deep Sea fishing, keys that will unlock special chests, or just a vendor that will take all of those Barbed Gill Trout off your hands and give you something worthwhile in return.