Speed runs make the game fun to me. Take it out or leave it active. Why should I have to hit a waypoint two floors before another in the game and run around everything to kill a boss when I can get there quicker by a waypoint closer already in the game?
I want to kill the boss ASAP and running around everything without killing anything makes it boring to me.
In Diablo 2 there were generally two floors of monsters to run through before being able to get to a boss, and in a lot of cases there were several monsters that needed to be cleared before you could fight the boss, either because it was required or because leaving them alive would probably get you killed.
The Diablo 3 system has apparently been changed so that you can only kill a boss if you're on the quest. If that weren't the case, it's unlikely that the closer way points would still be in the game. Also, we only have one data point that's not even an act boss, so I don't know how well we can draw conclusions from only the skeleton king.
I'm pretty sure that they did nerf the boss drops at some point. After killing skeleton king 12 times I got one yellow item total.
I don't think they nerfed boss drops so much as buffed the drops from random champion packs, which Blizzard has stated will probably be the best way to farm.
Also the boss system is similar to Diablo 2 where the first kill will give better drops. For example, the skeleton king is always guaranteed to drop at least one rare that first time that he's killed.
I think it took just as long or longer in D2. It still look a decent amount of time if you were doing tristram runs in a full game. Imagine playing the game without the help of higher levels and without years of experience playing. Might actually take longer in D2 if you were starting over.
Playing solo made leveling in Diablo 2 pretty torturous at points, but if you had a group is was pretty easy. Tristram and Tomb runs could easily get you to level 20 so you could do Ancients and start Baal runs. If you could get rushed, it was pretty trivial to quickly go through Nightmare and Hell.
Diablo 3 will probably take longer, if only because Blizzard probably hasn't left such obvious leveling exploits in the game. On the other hand, in some ways it will go quicker since it's no longer necessary to level multiple characters of the same type, unless you really want to.
And I'd bet the farm that it is a lot easier to get to lvl 60(if that is the max, I have no idea) than it was to get to 99
Getting to level 99 was an utter pain in the ass in Diablo 2 do to the way the leveling system worked. The more difference there was between your level and an enemies level, the less experience you would get. The highest level monsters in Diablo 2 were around level 85, so by the time you were at level 95, you were only getting some ridiculously low amount of experience for each kill (I think around 5%) such that it took hundreds to thousands of Baal runs just to gain a level and dying even once could wipe out several days worth of progress.
Level 60 will be something that everyone reaches if they play the game long enough. In Diablo 2, only the most hardcore crazies even bothered trying to get to level 99. Most everyone else generally quit in the low-90's when the experience gain starts to fall off heavily.