I wouldn't EVER go to a Canadian POE anymore to renew my TN. First time a couple of years ago, the officer spent a good deal of time looking for a confirmation in his computer that a bachelor degree was not required for Systems Analyst position. I didn't have my evaluated master transcript then and only attached a Canadian college diploma to my paperwork. Next year I was driving a truck to move my stuff to Florida and several immigration officers at the POE stared at me like I was a criminal or something. They asked me the same question when I said that I visited Canada on vacation and to pick up my personal stuff: "Why are you moving now, not before?" Like we are supposed to grab all our stuff and move to the States immediately after getting the first TN???? They searched my truck, didn't find anything unusual and let me go. I agree, every visit to the immigration is a Russian roulette, you never know what mood the officer is in today or what crawled up his butt. He or she can ruin your life easily and there are no repercussions to their actions. Though most are cool, some are real jerks and act like mini-dictators that make up their own regulations on the fly.
Some friend of mine travels to Mexico to get his TN and was never intimidated there besides having to stay overnight and wait a long line with Mexicans at the POE. I have been to Bahamas twice and have very good impressions there. Last time it took around 40 min (that made me pretty nervous actually) and the lady asked me extra questions about my college diploma. Though the diploma and transcript was from Canada and in English, she thought that it had to be evaluated in the US. But it went well and the officers were cool. No guarantee that it will stay the same in the future, it looks like getting TN status becomes a pain and the immigration tries to make our lives even more miserable.
But, honestly, I have no clue what the hell is wrong with Canadian POEs, why so many people like us who are invited by companies to work for them, companies that really cannot find someone locally... and we bring our knowledge and skills to the States, change our whole lives to the new venues and challenges, and just one day everything to be ruined by some immigration clerk???? We pay taxes, contribute to the society, abide the laws... do we deserve to be intimidated and humiliated????