Honestly, I can't tell if this is a good thing or a bad thing.
On the plus side, power supplies will be much simpler to design and test, with potentially better efficiencies. On the other hand, all those additional DC-DC converters will take up quite a bit of space on the already crammed boards, and now you got more heat to manage.
No heavy loads are connected to the 5 V / 3.3 V rails. Those are all supplied through the 12 V rail.
Though you do have a good point, nobody misses -12V and -5V.
Some of us (masochists) actually like RS-232!
Yeah, not only is 3.3V not guaranteed to be there, the latest rev of the SATA power spec reused (at least one) of those pins as a signal to inhibit spin-up; used for power sequencing in large disk arrays, with the fun side effect that if you've got a PSU old enough to have 3.3v on sata power, and you use a hard drive new enough to support spin-up inhibiting, you need to either tape the pin, or cut the orange wire, or you can't use your disks.