Mini-rant:
It's a bit more common recently, but since when did it start being ok to give 8.xx and 9.xx ratings out like candy on Halloween? Those are really high ratings that would place the track up near the most famous coasters on the exchange. If the coaster isn't that special, don't rate it like it is the greatest thing you've ever seen.
I'm not saying the ratings are bad, because most of them describe the creation accurately. But make the numbers match the words. This is a bit of an exaggerated example, but a comment like: "No problems, on a whole. Lots of pumps in the turns, and I died once from hitting my head on a prefab support." does not deserve a technical rating of 8.5.
So here's my idea for making the ratings a bit less varied from person to person. (because I have seen this on the low end, too)
Treat it like grading a college exam in engineering. This isn't you're grade-boosting microeconomics course that- as long as you show up and try you'll get a B. Call it what it is. A C (6.0-7.0) is average. A decent coaster will get that. But it takes something a little more impressive to get a lot more. Is the scenery is immaculate? Bring up the grade a bit. Maybe the supports are flawless... you get the point.
With the increasingly common usage of tools like Newton, the coasters will always be smooth. Unless it's a hand-made track that feels like this, don't rate like it is the only smooth coaster you've ever seen.
Make the technical rating more about how you used the program. Is the track all wibbly-wobbly, never quite banking to zero, or do hills have random radius changes? Things like this show that the program is controlling the track shape, not the creator. Tools are a way to make building easier, but they still require a bit of finesse. The same way that having an SLT doesn't make you a photographer, having newton doesn't make you the greatest NoLimits coaster designer to ever walk the earth.
The adrenaline rating can be kept pretty much the same as it is now, because excitement is a subjective matter. Still, think twice before rating it above 8.5, because it better be something special.
Originality/Accuracy should also be self-explanatory. Is the coaster pretty much the same as all of the other thousands of tracks uploaded to the exchange? Was that was their point? How did they present their creation? Was the picture they used to promote their coaster the reason you downloaded it? Maybe it was the words they used in the description.
All I'm saying is gain a bit of objectivity. I know it's a bit petty of me to rant about such things, but if all the tracks start getting 8 and above, the ones that truly deserve it will get lost.