1. You'll probably be stuck buying AC's lovely $2.00 plastic inflatable pillow/blanket combo pack. (They do offer "real" pillows and blankets on intercontinental flights
2. Somewhat painful. you will have to clear through Canadian Customs and pick up your bag then drop it off once you've cleared customs. You will need to transfer terminals.
3. You will get a complimentary hot meal. It's fine if you like airplane food. Otherwise, feed yourself in the AC lounge.
4. In LGA there is no Ac lounge but you may have access to either US or UA lounge when flying on AC if you are *G - not sure. AC has a very nice lounge in YYZ T1.