Perhaps I missed whether this has been the case in the past, but as chiko pointed out, the morning was predominantly water/hydrology/wastewater and the afternoon predominantly air. Since my area of practice is in air, that made for a tough morning (though a considerably easier afternoon.)
I'd seen suggestions that there are a significant number of qualitative questions on the exam, which is good since there are 100 questions. I actually felt good about the qualitative questions, since I do mostly regulatory-type work, and because I have a fairly good memory for stuff I read.
For what it's worth, having taken it, there probably wasn't a single question on the exam that was completely new material for me, or that if posed to me now, that I couldn't have a fairly quick answer for. If it turns out that I have to take again in April, I think just having been through once to get a "live" feel was good. It wasn't as grueling as I'd expected, I remembered more than I thought I would, and it was a good reminder that while the test is specific, it's not designed to be excruciatingly hard or to have complex calculations.
I also used a great tip from elsewhere on these boards, namely spending the first 5-10 minutes going through every question and assigning a 1, 2, or 3 to each. I found this helped me get a feel for what I knew and what was coming, plus helped me prioritize time. Since a definition question counts the same as a multi-step calculation, I wanted to make sure I got my low-hanging fruit first.