I have two questions that play a major factor in my purchase of this game 
 
1.) Is the ending as much of a negative as Brad indicates? 
2.) How well does co-op work?  Can both players play through the story at once or does only one progress?  Is the low difficulty mentioned in the QL even more of a problem with 2?

Don't know how it ends (and really, it sounds like Brad got a different ending than he wanted resulting in sour grapes, judging from the Bombcast), but co-op works very well. Whoever is hosting has the story/world progress, obviously, but anything building towards achievements, any gold earned, any treasure found and so on is either shared or duplicated for each character. Your own personal hero is brought in, too. I don't really find the game super easy, but since I paired with someone rather far in the game, he kind of tore people up for me, considering I'm still at the beginning.

Honestly about the ending and how the review described it, it just sounds like Brad was not paying attention. Before you go to Aurora they CLEARLY say the same things and give the same indication that you will not be able to go back the same way Fable II did before you went to the Spire. The characters make it painfully obvious that you should take care of anything else you want to do. What happens in the end-game involves you making decisions as the king and trying to balance the love the people of Albion have for you with getting enough money to protect the kingdom which may result from making unpopular choices. Without spoiling anything, the way Brad describes it, it just sounds like he rushed through the game and almost paints it that it's the fault of the game itself for what happened in his story. Take your time and play the game and whatever happens will always be the result of how YOU play it.  

Co-op is awesome, but only one player's story progresses. I'm not sure if completing a quest counts it for both players but I think you both get the Guild Seals (which is like XP) for it regardless. The game is rather difficult in general, much more so than Fable II which was ridiculously easy. It all depends on the players, their weapons, and upgraded skills. Even with everything maxed out though you always get mobbed by several enemies and the game plays a bit more reasonable (but not easy) when it's with two people.

so let me get this straight. (i havent beaten it yet, btw) 
 
after the "official" story ending, i cant go back and wander around in Albion like i did in 2? or did i misunderstand

Yes! You CAN go back and roam the world after the main story line is over! I just finished it, and it even appears to have opened a lot of new quests as well (small ones, no doubt). The game has a ridiculous amount of collectibles tied to achievements in it, so anything so ending the game Fallout-style would be extremely stupid, considering the save-system and all...

Here's a tip about the end of the game if you want to enjoy it after you've completed it. Make sure you have a lot of money before you become king/queen. And I mean a lot. Like 10 mil. That will make the end much better.
 
Hope I didn't say anything too spoilerific. Also, yeah, the end did really disappoint me. It just busts out of nowhere way too early. It's like a premature ejaculation, it leaves you ashamed and unsatisfied :c