Quoted from snaroff:
I've always used levels in the past (with ~30-40 other pins). Never had an issue. I guess I can try an old school test on a new fangled pin and ignore what the levels are saying. I'm curious, did you have any issues with "catch and release"?
The concern is that unless the level is exactly parallel to the playfield, the reading will be off. I have some very good levels but it has always frustrated me that there really is no way to determine parallel. Plus the accuracy of levels varies a lot. The longer the level, the easier it is to judge parallel. If you are using an accurate 12" master/starrett/similar level across the top of the slings, you have a much better chance of getting a good reading than the round one in your pic. Since most people don't have a $300-$1000 level, the rolling ball test is often the best way to determine level. (And I haven't even mentioned playfield twist where the top could list slightly to starboard, the bottom slightly to port.) Ain't nothin' easy.