I did electrical engineering at UVic (University of Victoria), which uses the same schedule as Waterloo. (As it happens, I actually went on to do a Master's at Waterloo, so although I didn't do co-op there, I'm familiar with their program as well.)

For me, co-op was an unequivocally positive experience. For one thing, as the OP says, school is stressful. More stressful than all but the worst full-time jobs. With a co-op program, you're only in school for four months at a time rather than eight, which really helps; it's a (relatively) short burst of intense focus, rather than a near-year-long slog. Yes you're moving every four months, but the trick there is just to not have too much stuff! For a four month visit somewhere, all you really need are some clothes (generally for only one season, so not your entire wardrobe) and toiletries, a laptop, and maybe a few odds and ends - chess board, deck of cards, whatever, and your phone. That's about it, really. You rent rooms in furnished houses, and just hold off on collecting too much "stuff" until you graduate. (Of course, you still do need somewhere to leave the stuff you don't cart around with you. Parents are generally willing to hold onto it, but if not, a storage unit would suffice.)
I've done several work terms with only what I could fit in my suitcase.

I've also found co-op terms to be a fantastic opportunity to meet new people. Ideally there are other co-op students working at the same company - people who are in the same situation as you, transplanted into a new city, looking for new friends. Even if not, there are often meetups for co-op students and that sort of thing where you can meet others from other companies. Especially in cities like Seattle and San Francisco! And sure you don't get paid vacation days, but... I don't know about you, but at least for me, coming from a term of engineering, even having weekends off without a mountain of homework to tackle was like paradise. It was absolutely a break. (And it's not like you wouldn't be working on your off terms without co-op! You'd just be doing it at Burger King or something.)

I was certainly lucky in some ways. My parents lived in Victoria, so I had a convenient place to leave my stuff when I left for work terms. And most of the companies I worked at had large groups of co-op students, so I generally had a good group of people to spend time with. But I think with the right outlook, putting in some effort, it would be possible to have a similarly good experience without those advantages. And then of course, there's this:

> The breadth and depth of the experiences, both academic and life, that I’ve had on co-op would never have happened if I was in a regular program.

Nothing compares to trying a new job in a new city every other four months. You're not necessarily knowledgeable enough through most of your degree (at least in hardware, as I was) to get a lot of technical experience from most work terms - although of course you get some - but what you get a ton of is experience with different types of companies and working environments. It really helped me to figure out what kind of company I wanted to work for, and eventually what kind of company I wanted to run.