I took the VCAP5-DCA test here in Singapore where I'm working this week.
This was apparently a huge mistake, since the datacenter where all the actual stuff is executed is simply too far away (latency/bandwidth-wise) to provide a usable environment. Everytime you click something, it takes 15-30 seconds for the information to show up on the screen, and some graphics never show up at all, just leaving a black hole or pieces of the old graphics that was displayed in the previous window.
This of course makes the test environment completely unusable. At least half of the time of the test (I had 4 hours, since I'm not a native english speaker) is spent waiting for screen updates, which not only wastes time, but also completely ruins your "flow". Don't even think about looking up some syntaxes in the PDF manuals, since switching the whole window to Adobe Reader and back wastes at least one minute, plus the time for each page change.
I told the local test center crew about the problems, and they agreed that it indeed was way too slow to take the test, and called the tech support at the datacenter site. They said there was nothing wrong with the central equipment, and asked them to change my workstation, which of course didn't help. Then they gave me an extra 30 minutes, which in reality didn't help either. This was probably the fastest 4,5 hours I've spent in a long time. 
One of the tasks was too weird to understand what they really meant, and three of the tasks I couldn't finish due to errors that I bumped into when trying to do the steps described in the tasks. I think they were bugs or misconfigurations, but they might also be because of something I messed up myself.
I think I finished 19 or 20 of the 26 tasks, but maybe not all of them correctly, so I really haven't got a clue on whether I will pass or not.
There, I had to get this frustration off my chest.