First off, congrats on your offers! all four programs are great. I had the same options as you in high school (ME instead of EE/CE). I actually went to two of the schools above and have many friends in the other two, and have spent time at all four campuses. All four schools have their own unique strengths and weaknesses, and its ultimately up to you to see which one fits. That said, here's my analysis:
1) Waterloo CE: If you want to make 100k+/year working in silicon valley, then this is the way to go. The school's co-op program is the best in the country. They are notorious for placing students in Facebook/Microsoft/Apple, but you will have to earn it. The program is very difficult, and has a high failure rate. For every Facebook-type kid i know, I know 2 more that dropped out or transferred. College lifestyle (especially in CE) is definitely the most lacking out of the four, and most likely you won't have time for it.
2) U of T track one. The top tier jobs are still available to the top students, and the program is not as stressful/difficult as Waterloo (still very difficult). You can have a social life if you are very organized. U of T is located downtown, and as a person, you will have to love living in the city being surrounded by people. That said, the bars/clubs are great, but you'll have miss out of the traditional college experience. But be glad your not in Eng Sci
3) Queen's Engineering. EXTREMELY FUN with great people. For an engineering program, this is the closest your gonna get to the college lifestyle you see on T.V. The program is still challenging, but definitely manageable and the easiest out of the 4. Relatively easy to get high GPAs. Great campus and athletic facilities as well. The biggest con is that the main industries that recruit here are Oil and Gas/Consulting/Finance, and not many people go to top-tier software/hardware (a few still do). Local recruitment in Ontario is still decent. If your goals are truly Hardware/Software in the U.S, then it pains me to say that you should go somewhere else.
4)Mcgill EE/SE/CE. Balanced pros and cons compared to the others. Lifestyle is top-notch if you love the city. Drinking age is 18 and the bars/clubs are phenomenal, but you do miss out on the traditional college experience. Like U of T, you will have to enjoy the city. Going into U1 has its advantages, with less course load and potential to graduate in 3. You are right that switching faculties is difficult. Placement into top software/hardware jobs is decent, although not as much as waterloo and you have to be a top-tier student.
So in conclusion, If you are gunning for silicon valley and is willing to work through hell, then go to Waterloo. If you want balance for career/life, then go to U of T or McGill (you seem to like montreal better so i recommend McGill). If you want a great social life and is willing to consider other industries, then go to queen's.