I've had various problems with them in the past, and the present, just realized the oil cap on my 462 was leaking this morning. But most of the problems I've had on them were somewhat self inflicted, not getting the cap on properly or as with this one most likely because the saw/cap is dirty. They aren't the worse design in the world, but they are overly complex, especially compared to a husky flippy cap.
As for the 038, if you have to keep on the throttle, something is wrong. A saw with a plugged vent will usually run fine for a bit, then as negative pressure builds(a vacuum) in the tank they start running like crap until they shut off.
What were the initial symptoms of the saw.