^Optimism101, are you sure there isn't something in the contract saying that they reserve the right to increase the interest rate above prime? Ignore what you were told verbally, and look closely at the fine print.
Shady, I signed with Scotiabank, and they have an "adjustment factor" that is added to the prime rate to determine the total interest rate they will charge. Currently, the adjustment factor 0.00%, but they state that they can increase this adjustment factor if they wish. I asked BMO, RBC, and CIBC if they had something similar in their contracts, and all of these banks said yes. So it appears to be standard. Also, to ease anxieties, I was told that it is extremely unlikely that the banks would increase the rate above prime (of course prime itself will fluctuate, but the banks cannot control that).
For those still shopping around, I strongly recommend asking for copies of the contracts BEFORE submitting applications (since multiple applications decrease your credit rating).
No worries though, as I think we will all be just fine.
Edit: I didn't mean to have the smiley face in the subject line lol