As an aside, I think TN status is great if you can get it. The only real problem is that you lose it as soon as you step off of US soil and have to re-apply when you try to re-enter. This makes for increasingly stressful trips home to Canada (or Mexico) since the longer you are in the US, the less likely you'll be given a new one when you return. Granting the TN is totally arbitrary and depends on the mood of the border agent and the quality of your paperwork. Make absolutely sure your job title and description is identical to one of the TN-permitted ones. Lawyer-up if necessary. The cost of getting lawyer to prepare you is more than offset by the increased salary available in the US.
I've talked to people who've done it, but you can't leave the country when you start the process. It's better to use an H1/L1/etc. As a Canadian, I wouldn't really suggest US citizenship although.
Which isn't that bad. If your company is keen on having you stick around they can do the TN1->H1B->Greencard juggle in under a year. Otherwise, just sticking with your TN really isn't that different from being on a Greencard. Yes, you have to renew it yearly and the immigration folks can be surly about it, but you pay your $50 fee and you get another year. I did it for 10+ years without issues.
