Very true Sharke. In most situations, you have 15-20 seconds to size up the situation. That may not seem like much, but it's enough for you, the owner, and the dog to establish a position. If it's going South, most owners put the dog in a room, or otherwise contain him. More often than not, the dog picks up on the vibe from its owner that I should be there. Some get a little too comfortable, and it is difficult to work because the dog wants to put its head in my lap

. On many occasions, dogs that don't normally agree with strangers have been incredibly comfortable with me, and shocked the heck out of their owners.
Pits can go either way, but as you say, they are very strong. If they are comfortable with you, it's probably an ok situation. If not....
I don't do Dobies, period. They are predictable and not good. Same with Rotts.
Labs, Collies, etc are fine. If you get on the bad side of those, you probably deserve it.
Little dogs are generally more scary. You're right again, Chihuahuas can be a real pita.
Fortunately, boots and loose fitting pants are a good defense.
On positive note, I played for about 30 minutes tonight. It hurt like hell, but it felt good.