Jup, to my understanding the head is a minute amount inclined, this is some importance with carbide insert cutters. They are not big on rubbing (on the back stroke....)
No, there are two different distictions on here:
* Quality of the finish, ie smoothness
* Geometry: trueness, flantness you name it
They are little different, not although completely different.
Peeple like fly cutting, because that produces uniform finnish and on quite a few cases little concave part is easier to mount without rocking. But larger the cutter radius, bigger the effect of head/quil error is. You can see this if you face a surface with end mill may times over - it looks untidy, but when you blue it it does not look far off. Then again if you fly cut face on one go, it looks rather convincing, but it bears only on edges. How importat that is depends completely on your needs. THen one thing is spindle "float" - if th spindle bearings etc. are not rigid and only with minimal play cutting forces tend to "lift" the cutter, noticeable at the start and when you change cutting direction - adjustement, power feed and dicipline helps here. I try to cut to a most flattering direction when I can.
This is an advice of relatively unexperienced, threat it accordingly.
Pekka