just finished the trip 2 days ago

I just drove the same drive, but farther on both ends, a few days ago and had absolutely no problems. I only had my car full, but it was packed to the brim and they didn't want to search it at all. I've also done the drive with a van lines company moving my stuff up to Canada from NYC and I never had problems either and they never went through any of my stuff. I'm also not organized enough to ever have anything written down as to what I own, but then again I bat a mean eyelash, so that could help!
I would say it is definitely worth it to go down through the states! Gas is sitting at $2.5Gal. Which is way cheaper than anywhere in Canada and Motels are being advertised at $39.99 a night. Plus I don't know if you've ever done the drive over the great lakes, but it is a windy, one lane highway and you might end up sleeping in your car at a gas station in Wawa, Ontario for fear that if you continue you will not find a gas station open past 8pm that accepts plastic!
Only talking from experience, but thats my two cents! (plus then you can go to the Outlet Mall in Albertville just north of Minneapolis-its the biggest, best outlet I have ever been to!)
Good luck and happy driving!