I drove up earlier in the year with a bunch of stuff because I didn't know how long I'd stay. I'm Canadian but a permanent US resident atm. No problems at the border in either direction.
Well, maybe..... when I was coming back they asked me what I was bringing back that I hadn't taken with me and I'd drilled out a couple of sticks on the drill press at my parent's place (y'know, mod stand kind of thing). They got concerned about the wood I was "importing" into the US. Seems they don't want you to transport untreated woods for some kind of disease transportation concern. I had to get out, pop the trunk and open up the bag with the little pieces of birch or poplar or whatever it was. The customs guy realized that we'd been talking about completely different things and was happy to send me on my way.
My lesson for the day - don't park too close to the guy in the cubicle - it's hard to get out of the car and even harder to get back in (curbs and all that).
Oh yeah, no problems with any of my devices or liquids - they didn't ask, even though I had, probably, a long eGo jutting out of my pocket at the time - there were more substantial mods in the passenger side but nobody asked anything about them.
A rather big heads up - no radar detectors allowed in Canada - they take a dim view of them and you won't get one back (no personal experience here). I just leave mine at home where they're safe.