Unless your code is entirely parallel, which is impossible in most cases, the serial portions will dominate performance as the number of cores increases. As such, better serial performance is critical to improving the scalability of even highly parallel workloads. If you want more information, this limitation is known as Amdahl's Law.

Calling it a waste of time is quite subjective. For those whose idea of playing a game is simply to burn through it as quickly as possible, sure, it's a waste of time. But for some, it's not, especially if the game is a platformer. Could you imagine if every time you fell into a hole in a Mario game you simply respawned right next to it? There goes the joy of learning to skillfully navigate the levels.

Uh, perhaps because many games simulate things as complicated as driving a car? If you ask me, leaping from wall to wall to triple backflip somersault, etc. should require at least some skill to perform. Don't get me wrong, I like it easy now and then (I do own a Wii, haha), but if all one looks for in games is cheap thrills, then yeah, all games should be beautiful walks in the park. I was surprised by PoP's direction in this game, and the amount of forgiveness it has for errors turns me off a bit. And it's not as if making your game easier and improving the controls is some new, unheard of "innovation."

Well, as a cellist, I can say that vibrato definitely has pleasing effect on the ear, and allows for extra expressiveness (through varying types of vibrato, fast/slow, wide/narrow, etc.). And you can't fake intonation, vibrato or not. Of course, I'm no expert in vocal music, but I would think the idea is similar.