When I first started playing WoW I lived on a PvP server, I'm quite fond of world PvP and I did enjoy it for a long while.

However once I hit 35ish and STV I spent more time dead than alive. Mostly from level 60s ganking.

Now I play entirely on PvE, I get as much PvP as I want either in Outlands or in BGs (not tried arena yet) and can level where I want in peace.

So:
PvP is good.
Ganking is bad.