I'll be the first to admit. I was not ready for the PTR. The issues caused by Blizzard are the easiest to deal with. I'd hate to see what Big Bear Butt would have to say about the asshats.
So here are my top 10 reasons the PTR sucks.
10. Hey I'm on the PTR, nvm it just crashed
9. Hope you like the default UI, because yours won't work
8. If you personally can't double for Fort Knox, don't plan on buying anything
7. People who are there only to flex their epeen
6. Raids will disband after one bad pull, even when no one dies
5. Players decide that they are too good and don't follow simple instructions (Don't beat on the damn gargoyles when they are stoneskinned)
4. Test Forum QQ
3. Ebon Plaguebringer stacking is still bugged
2. Asshats galore
1. My friends can't make it past the copy queue
If you plan on copying a toon to the PTR I highly recommend you ask your guild to loan you its bank contents for consumables, mats, and gold before you copy over. Then copy your toon twice to double that up.
Bring as many of your friends as you can and tons of patience. Dealing with the bugs and crashes will try Mother Theresa's calm. Throw in all the nastiness and it can get unpleasant.
Hang in there though. You will find a few diamonds in the rough. There are good people there and there are bugs with the talents, dual specs, new UI improvements and there are plenty of opportunities for quality feedback to make the game even more fun.
Finally, have a plan for being there. Mine is to test a dedicated tank and DPS spec. So far Unholy hasn't changed much from live and from a DPS perspective swapping Gargoyle and Unholy Blight doesn't have a huge impact.