I generally go there a few times a year as well. The best exchange rates will usually be pulling money out of an ATM when you get there, but I rarely ever get cash. Unless you are going to places where you would definitely need cash, credit card acceptance is extremely high. Amex will be hit and miss (most chains and larger stores will take it), but Visa/MasterCard is near-universal. You WILL want a contactless card (referred to as "tap" up there) or mobile wallet if you want to avoid strange looks handing your card over outside of touristy areas, and then the even more awkward time spent waiting for someone to find a pen for you to sign the credit card receipt with like it's 1985. 
Not sure if you are driving or flying, but if you are driving and have Global Entry, bring your card as it allows you to use the NEXUS lane coming back into the US as long as everyone in the car has it. You need an actual NEXUS card for entering Canada using those lanes, however.
I have little/nothing to offer beyond what's been written above.
I bank with TD Bank in the U.S. (and have their TD Cash Visa card), and TD Canada Trust in Canada, so I'm pretty much covered for a decent exchange rate. I'll emphasize the no FTF comment.
@K-in-Boston wrote:
Not sure if you are driving or flying, but if you are driving and have Global Entry, bring your card as it allows you to use the NEXUS lane coming back into the US as long as everyone in the car has it. You need an actual NEXUS card for entering Canada using those lanes, however.
Thanks K! Wasn't aware of that, Canada I figured was a little too close to home to visit but it might not be a bad spot to hole up for a month in my "working from home" world tour if scheduling permits. That tip might come in handy if I road trip it.
Don't confuse kilometers per hour and miles per hours, that can cause you to have blinky lights behind you!
