so true. I have learned from the start to cut rectangles/squares but the other day I had to fabricate a patch for a quarter that someone else cut out. It was cut out like a Nike Swoosh logo. It was pretty difficult to trim up so I stopped myself from perfecting it while holding it up to the hole so I left it a tad long and just started tacking and shaving as I go. the weird shape made it a nightmare to cut and match.
edit: I guess I should note in my original post when I said "complex shapes" of the patch I'm talking about the contours of that area, not how you decide to cut it out. I always try to cut it out the same, as a rectangle or square, with slightly round edges.