I overwhelmingly agree with Jim here.
Locking players out so they can't play unless they pay is despicable...UNLESS it's done properly, which is next to impossible.
There are games where it's done right (Fallen London does it well), and in most of those games, the wait times are both reasonably small and the game is designed to be at its most entertaining when played in small, spaced out bursts so you don't mind not being able to play more for a while. Then you come back in a half hour or so, play some more, etc.
But the overwhelming majority of games that use free-to-wait are absolutely awful.
For example, I played Spiral Knights, a Free-to-Wait MMO for a while. At first I was massively annoyed at it because you only get 100 free energy per day (slowly over time) and it costs 10 energy to go down one floor in the dungeons. So I stopped.
Then I picked it up again and found that it wasn't that big a deal, really. When I was out of energy, I usually felt done with the game. I even let the use-energy-to-revive mechanic slide since if you played with other people they could revive you for free anyway.
THEN, I got far enough into the game that I really needed to craft stuff. And then I found out that crafting equipment requires energy. But alright, I decided to use my off days when I couldn't play to craft equipment. It was here that I started getting really really annoyed.
And then, I hit the point where it takes MORE than 100 energy to craft stuff. I asked on the forums if I literally could not progress any farther without paying and was told to use the in-game currency to buy the Paid Currency (crystal energy) via the player-run market in order to forge stuff. And of course, getting the amount of in-game currency to buy one shot (100 CE) of paid currency requires multiple (At least 6) dungeon runs, or several runs of this one boss that drop a ton of currency (I think you can guess what dungeon run is the most popular).
That did it. That was the thing that finally killed it for me. I just could not put up with it anymore.
It also doesn't help that the market for Crystal Energy is entirely player dependent, so rates fluctuate weirdly. Although the trend seems to be that CE is going higher and higher over time, which just makes the whole problem worse...
The devs DID try to mitigate this a bit by letting you "pay the tab" of other players at elevators so you could carry them with you on your energy supply, and other stuff like that, but overall...It just made me really weary of the whole thing.
If Energy wasn't required to craft shit, I'd probably still be playing Spiral Knights even WITH the limited amount of playing time per day. Because I really liked it. Once in a blue moon I'll load it up to do a run, but unless things change seriously, I don't think I can ever play it seriously again.
In the meantime, I've gotten into League of Legends, which does Free to play well. I can play as often as I want, as much as I want, and even playing only one match a day, I've gotten enough in-game money to unlock basically any character I want at the moment. I literally only bought ONE champ with real money in the past 6 months, and the rest I earned with in-game money. Now I have a decent enough champion pool that I don't really feel the need to buy more.
As for Dungeon keeper...24 hours to mine ONE GODDAMN BLOCK? What kind of !@#$wit thought that would make for a fun game?