As long as the game was built with a subscription model in mind to begin with, I'm okay with it. Even when those games inevitably go free to play, there will still be the option of keeping on subscribing without losing access to anything.

When I play a game, I want to have full access to it. I want to pay a certain amount of money, and then never have to worry about nuances in the service being provided. In The Old Republic, I could go on as I did before when it went free to play, so that was fine with me. In The Secret World, the item shop offers some shortcuts that aren't needed. I've paid for these games, and I get unrestricted access to them as long as my account is in good standing.

In a game designed as free to play from conception, there is always the spectre of the cash shop hanging over you. I have no idea what sort of baseline the developers are aiming for, but I suspect they want players to spend at least the equivalent of a month of subscription for another game in their stores on average each month. This doesn't sit well with me; key features are often expensive, and even if you pay to remove one restriction, there will always be another taunting you, and that's not even getting into the sheer audacity of putting cash-shop only progression consumables there. Having to constantly be reminded that your equipment could be much, much better if you shelled out a bit of cash ruins any sense of progression in the game, and knowing that the game is built around the expectation that you buy at least a few of these per month just kills it completely for me.

All that said, I'm fine with a cosmetic cash shop existing, as long as it doesn't overshadow customization earned from gameplay.

In short: I want to pay a fixed amount and then just have fun. Make me pay for the service, not the parts.

I don't know but I guess that the development costs are much higher than the hosting costs. You could probably still calculate with a one time payment, only that would look more expensive than a subscription.

I probably spent at least £400 on WoW membership, but I know damn well I wouldn't have paid that up-front...

I think it depends on the game, Some games can survive on a P2P basis, EvE is a great example, last time I looked at the figures subscription numbers were going up. (how many are new players and how many are alts would be interesting though)

Other games seem to need to go to the F2P platform to survive and use micro transactions to fund them.

And then there are the ones in the middle such as Fallen Earth that are F2P but you can optionally pay a subscription and you get benefits from being a subbed player.

I think in the end all mmo's will eventually go F2P but there will be differences on just what is available to free players or that free players will be penalized over the subbed players.

If I were to play one of these MMOs, it would be Guild Wars 2 or one of the F2P games. If a game has a subscription or micro/macro transactions I want nothing to do with it.
I played the original Guild Wars, and while I enjoyed it...I felt the game was a little boring. It seemed like the game world was big and empty.. Perhaps the multiple expansions filled some of that emptiness, but I didn't purchase any of them.