Yes, midrises are appropriate on main streets like Laird, Bayview and Eglinton. But we should be looking to encourage the transition from midrises to single-unit dwellings by having townhouses, duplexes and multiplexes in between. This way we can continue to build density beyond the midrise.
I know this is addressed to ksun, but to address your first concern, that is the point of the 'missing middle' housing I pointed to above. They maintain the build form and character of low-rise, single-family homes while adding more dwellings per acre.
We want to encourage density because density helps local businesses, encourages restaurants, supports local services and public transportation (a lowrise single-family home build-form cannot support public transportation on its own, but the 'missing middle' housing types increases density of low-rise areas to meet threshold for viable public transport), and because more people in the neighbourhood means more security and safety by virtue of having more eyes and more people walking on the street going about their business.
We as a city also have growing demands for density as we want to encourage development along transit corridors like Eglinton. We've been focusing purely on building highrise condos so far to meet this density, and we have an official plan encouraging the building of midrises along our avenues, but these are not the only solutions. Certainly for an area like Leaside that wants and should maintain its low-rise build form, zoning can be amended to allow the construction of denser low-rise housing.