First of all, in my opinion, you should remember that stats are only numbers and to some extent, somewhat useless.
Not to mention that some figures look better than the others and there's always a need to have the best numbers for the eyes that need to see them.
Then, regarding TN applications at the border, stats might not include those applications that have been verbally denied therefore a 97.3% might look unrealistically bright.
Also, please keep in mind that border officers have the discretionary power to deny a petition.
My experience with getting a TN at the border is bad. I've tried to get a TN visa at 3 different POEs (Sarnia, Buffalo Peace, Thousand Islands), same application but different letters of employment (ie different dates) each time I applied.
The worst = Buffalo and Sarnia. Even if I requested for a TN officer to review my application, regular, less experienced, impolite (should I say rude?) officers were assigned to my case and reviewed it. While I was there, I saw other applicants arguing and being denied. A friend of mine who applied the same time at the same place with me was denied her Accounting petition because the officer didn't want to recognize her advanced (graduate level) accounting degree and her experience (her bachelor was in Economics, and should have been recognized but this is another story).
At Thousand Islands, the TN officer just retired ... .
Rude behavior examples? "We ask the questions and not you." when I asked why they didn't want to recognize my work experience obtained before and during the period I earned my degree. The law doesn't mention the required dates when the experience was earned relative to the degree earning date.
Another one
"If you deserve it, I'll give it to you." - my accountant friend is a good looking blonde.
We both got our visas at Detroit Tunnel. Here TN officer was professional (as all border officers should always be). At my first attempt I was verbally denied again (the 3rd time) because I did not have the original evaluation of my degree only copies. I then returned the next day with the same application and the original evaluation document and the TN visa was granted in 15 minutes.
Please don't feel discouraged by my experiences, I might have had a bad Friday 13 luck.