How is PvP on PC?

Got a couple of questions about PC PvP:

1. What are the lvls at which frequent PvP happens as well as areas?
2. What is the quickest way to get PvP going? Red Eye Orb invading, Cat ring invasions, Blue Eye orb, Red sign?
3. Any particular builds to go with or avoid? At the higher lvls (~80) I've noticed quite a few people going heavy armor and using Dragon Weapons' special attacks. Is it really that common or just my luck?

I don't have much time to answer every question, but I get nice PvP in the following areas:

1) the Forest, any level, both as invader and host
2) Anor Londo, at around level 50
3) The Depths at around SL 20-30, darkwraith invasions... I get nearly constant invasions each time I use the orb.
4) Tomb of the Giants at SL 100, using the red eye orb. With a bit of patience you can invade several people.
5) Oolacile Township, SL 100-120. The problem here is that....well, I'm not sure if this is a honorable dueling area in PC, unlike consoles. Basically I have met more honorable people in the Forest than here, and that's saying something....you get spawnkillers, people that attack during bows, gankers, etc.

Go forest if you go high on level,
Township if you are staying at sl 100 range
Anor Londo or Sens at 51
FC 100-120


Beware though you will meet plenty of assholes sometimes