6A12 MIVEC weaknesses?

[spetz]

What is the weakness of the 6A12 MIVEC?

By weakness I don't mean if you pump 20 pounds of boost into it, but rather what could have been done better from factory?

For example I think I read somewhere that there is some oil problem inside the engine? ie oil supply gets bad to some area of the bottom end?
Maybe near the main end bearing?

Also heard that with ignition coils, and o2 sensors get problems. TPS seems to be a common problem.

Otherwise what else?