Sure. These are my issues with the event.
Like Umaroth said somewhere earlier, luck is a huge factor with the devices because most of the top teams are able to build accurate temperature sensors. However, a lot of variation can come with factors, such as where you place the probe end in the water or timing. In hot water (such as say, 70C), I have found that moving the probe from the bottom of a cup to the top can result in a change of about 1-2 degrees - which is a pretty significant margin. Also, note that time can definitely factor in to the situation - for example, your device may be 0.1-0.0 degrees off 95% of the time, but then the weird probe that the tournament is using lags behind for a second and suddenly luck has made the difference between the probe and your device 0.2, while other teams didn't experience this. I understand that the devices at nats are all supposed to be pretty good, but like this is ridiculous - I mean, it's just luck between the top teams at this point.
The design log is basically free points, if you do it. Most supervisors just scan over the info, and the design log doesn't even make sense in a variety of ways. For example, what's the point of showing your equation on a physical graph when you may just change it during the calibration period anyways?
The LEDs are obviously easy to get as well - this basically just comes down to simple wiring and coding skills. Literally something along the lines of " if (T > 20) { redLED(true); greenLED(true); blueLED(false); } ..."
The parameters for the test are four bullet points in the rules. I don't have a huge problem with this, but considering that in many cases this has been what has broken some teams apart (such as Princeton), it would be nice to see some more expansion in this section.
Also, this event really needs some clarification on what is allowed and what isn't allowed. This caused a lot of confusion and FAQ's this year, and caused a lot of frustration when a competitor was told that the piece they were using was no longer allowed. Just my two cents.