I've noticed the scraper thing while doing my violin.
The thing about going backwards with a router, isn't that common sense? I learned that LONG ago. It's pretty noticable when you are rounding over egdes to go backwards in some areas. Basically, look at the direction of the grain along the shaping of the body's edges/sides, and how it relates to the router bit. The router bit is no different that any other cutting tool, such as a chisel, and if you cut against the grain, you will most likely get tearout. Obviously with a router you can't re-orientate the piece to cut with the grain (unless you want to flip over the body and reset your temps), so you must go backwards.
When you do go backwards, however, and especially when doing sides, make sure you have GOOD control of your router, or body, depending on how you are cutting it, because the bit will 'grab' when going backwards.
Myka's tip is very good. I think the 'shear' bit he's refering to is also known as a 'rake'. The cutters have a positive 'rake', or angle of a few degrees (I've seen some with 4 degree rakes) to them.