I leveled up to 200 without using doubler (except for those Mulled Wines we got for Christmas).
I prefer PvE and usually only PvP for friendly competition unless the benefit of winning is too great to turn down. I never bounty a bounty hunter since they're just doing their job.
My favorite form of revenge for a PvP attack is waiting until someone has logged off for a few hours and then placing my bounty on them when they aren't there to let people know someone has already taken their bounty.