Your friend's experience prove

that's O.K. and many others did that the same way, especially white guys.

Pro: Fast, Can renew TN, even lose job, you two can still be back Canada to wait GC.

Con: Without EAD/AP benefits, has to keep TN/H-1B to work, may not that safe as I-485 way (in terms of denying, you can't appeal CP decision, but I-485 you can.)