The best PC bowling game was Brunswick Circuit Pro bowling from the late 90's. The graphics aged poorly, but the pin physics were the best. I have tried every bowling game on the PC and have bowled thousands of games in real life.
The latest on the PSP has very good pin physics. After about 6 hrs of playing, I'd say the pin action feels right about 85-90% of the time. About 5% of results are just strange.
People who bowl often can predict with a pretty good accuracy what they will leave before the ball hits the pins, and this is where the % comes from.
The game's biggest problem is that the pins are too stable during the secondary collisions. (eg. A pin rolls into or comes in contact with a standing pin.) This must be a compensation for a lack of realism during the initial collisions. Initial pin action is good though.
(Yes, I'm a physics nerd)
As for the oil breaking down, so far on league pattern it's subtle at most.
People might initially complain about high scores being easy, but on different "league nights" the oil seems to be slightly different than the night before, plus your character's attributes change which means you have to find your strike zone again. This has been more than subtle.
It would be nice if the game had additional play options and the career mode is just adequate.
I also think them going "vertical" holding the controller at 90 degrees was excellent, but why does it go back horizontal after the game is over?
The FUN FACTOR: Probably on the low side. It's a bowling Simulator. I'm going to try out the Wii version this week (which has been hammered in reviews because it's not Nintendo bowling.) Wii Nintendo Bowling is like beginner bowling with your friends on Saturday night (with higher scores). Brunswick Pro is like a serious league night.