If I remember correctly, when you are the Resident then you can decide to not allow the vote for the religious victory. Also if you are a large voter you can abstain and there will be insufficient votes for the other civs or you to win. So if you think winning by the AP is cheesy you can effectively stop it by taking control and stopping anyone from getting that victory, including yourself. I'd say that was an additional challenge rather than making the game too easy. The AP is a great game feature in my opinion and a major addition in BtS.
This is true. However, you don't even have to call the vote. You can just pick the "no action" option or whatever. If you're the AP chair, it's impossible to win this way if you don't want to. If you're not AP chair, you probably don't have THAT commanding of a lead in the religion, though I could envision some extremely rare exceptions.
You also don't have to go spreading it around if you don't want the win. Accidental AP wins are rare...I've only had one and it was after I'd wiped out everyone but a friendly civ and his vassals, capturing the AP in the process. I didn't even spread the religion in that one, but I'd captured more cities than the remaining vassals had, and my only competitor liked me and wasn't in that religion. He had more votes than I did and voted me a win. Even then, I was willing to win that way, or I'd have not called the vote.
Every other AP win for me has been intentional, and in many cases schemed (aka capturing the AP and using it to win, or building it early in a rare religion...typically christianity but occasionally something like taoism or confuc.)
Does everyone actually view this as "cheap" instead of just "powerful"? Not only do you have to have it, you need 75% votes. You have to pick a religion to get someone to like you, without getting killed. You also need OB with everyone or you'll have to go to war anyway, and if you spent too much effort on the AP that might be harder than normal, although you can probably draw some religious allies into the fray at least.
There are lots of strong wonders, like the mids really turbocharging the SE and making games a lot easier.
I agree that the AP makes the game easier, but often if you clear the diplomatic conditions necessary to win using it (aka someone ultra friendly with you and people not killing you), you can usually last in the game long enough to win other conditions also. I had a game where my AP attempt failed (PYL III, actually), but the diplomatic leverage I'd set up was more than enough to pick civs off one by one until I was the largest civ on the planet.
IMO it's not any cheaper than buddying up with a strong AI and teching to space, or winning via culture.