I just got invited to Beta last week.
They only allow you to go to level 83 in the beta, and there are basically two zones you can choose to start your leveling process in for quests.

There are a couple of very frustrating quests where there weren't enough mobs for the number of people trying to do the quest (under water zone - kill 8 sea serpents, so it would work for a group quest fine), but the problem was there were only 6 total sea serpents in the area and about 5 people trying to do the quest at the same time and the respawn rate was about 5 minutes.

I did put a ticket in on it since we WANT kill quests for us boxers, but looking forward toward this the first day of Cata will be a nightmare --- maybe even the first few weeks.

The good news is that I leveled from 80-81.5 in about 4 hours.