I myself have taken my laptop w/ me on my most recent trips. The only hassle that I have had to deal with was that I was asked to take it out of the laptop case and put it onto a tray separately from the rest of my carry on items. Fortunately for me, I have not been asked to power it up for whatever reason.
As for your return to the US from Montreal, expect for them to carefully scan your computer with a special cloth/swab that could detect traces of specified chemicals/explosives. They also asked me for my boarding pass in all of those instances, and then they typed something into their computer and said, "OK, here you go. Thank you," and off to the departure I went.
As for hotel charges, Special K was very detailed with his description.
Hyatt charges $9.95 (before taxes) for high speed connection in your room. Otherwise, you could request to use the computer lab for free for 15 min. or less.
Delta Hotel is free connection in the room, usually in rooms on floors 16 and above.
Hotel Suites Le Faubourg has free hi-speed internet connection.
Four Points Hotel offers free connection if you wireless capability with your laptop, i.e., you need to have/purchase a wireless PCI card. (I recommend you buy this card to give you wireless access to the internet.