While the tech scene isn't as hot as the other regions you mentioned, it's still strong. Very strong. It's also starting to be noticed by the bigger players (with Google and Apple both investing in the region). Currently I'd say the biggest weakness for tech in Toronto is the financing side, with the traditional financiers being very focused on revenue and getting cash flow positive early in a company's cycle (a very Canadian, risk averse business culture), as opposed to the riskier but higher reward models favoured in the valley. But the greatest strength is easy to spot: the city itself.
It would be easy to argue that Toronto is the most cosmopolitan city in the world. The standard of living and quality of life are very high, and widely recognized by publications such as The Economist. The diversity in the city isn't just surface deep either: Toronto boasts one of the most diverse economies for a large city in North America. The strong tech industry sits aside a very strong finance industry, media industry (tons of television shows and movies are produced in Toronto), fashion industry and others. The way I like to explain it to people is that Toronto is not the best at anything -- but it is among the best in almost everything.
So there's lots of work. The other ingredient is that there is also lots to do. The strong cosmopolitan nature of the city means a dizzying array of options for dining. Those options are not just the affordable "ethnic food" you typically think of, but run the full gamut from affordable and delicious to some of North America's best fine dining. To that you can add world class museums, excellent (if under built) transit, many interesting bars and cafes, housing that's quite affordable compared to the bay area (I own a townhouse close to the city centre), hot summers and reasonably mild winters, government provided universal health care, and so on and so on.
So yes, people definitely do move here to join the tech scene, but not people whose ONLY consideration is the work they do everyday. That's an important consideration -- perhaps THE most important consideration when looking for a place to live, but it should not be your only consideration. Once you start to add in the other factors Toronto looks fantastic.