I am a competitor (did 7 comps last year, will do 10 this year) and a KCBS CBJ (judged 4). I will tell you as a judge, it is the hardest to judge. First of all, you are full and overwhelmed by all the meat you have eaten in the previous 3 catagories. Then the most filling meat comes to you to judge.
What I have noticed about brisket is often they all taste so similar. If you want to do well it needs to make a judge notice it, be different. I have heard many judges comment, "here comes the dried up pot roast." when it is time to taste brisket. Unfortunately there are a lot of briskets turned in that taste that way by the time they get to the judging table.
Just my 2 cents. Brisket has got to look great, be perfect in the box, have perfect texture, not be dry and most of all taste awesome. Not hard to do, right???