I'm sure there are better forums to get good answers but here's my 2 cents. (There's a forum called "Grasmick" that deals with Canadians working in the US that might have more info although it's primary focus is work permits).
Offhand I can think of a few issues:
Schooling : We've been to a few campgrounds in Florida during vacations and I was shocked with the amount of kids that are either homeschooled or going to school in the area (There appears to be a fairly significant population of families that migrate to Florida in the winter (from Northern US - I didn't actually meet anyone doing this from Canada), live in campgrounds (and presumably rentals as well) and spend the winter there). Although academically, kids can do better with homeschooling (more dedicated attention and progressing at their own rate), IMO, they miss out on a very important part of education which is the social aspect so I'm not a huge fan but that's certainly the easiest thing to do. I haven't really looked into it but I don't believe that as a Canadian you can simply move to Florida for the winter (i.e. as a tourist) and register your child in public schools. I believe that you can only do this if you have some sort of residency status (e.g. temporary work permit) but it's certainly worth exploring. I suspect there's no restriction registering in private schools (although that might be quite expensive (e.g. as expensive as going to college).
Healthcare : As long as you maintain your Canadian Residency and are in Canada more than 6 months per year, you keep your provincial healthcare. It would still strongly advise to get supplemental health insurance but it's MUCH cheaper if you are still covered by Ontario or whichever province you are a resident of but that still might be a noticeable amount.
Work / work authorization : You'll have to do some homework on this and I'm not an expert. Even if you don't have US work authorization, there is still some work that you can do in the US but there are some contraints. If you work for a foreign company (or have business in Canada), you can do the work in the US without a work permit as long as it's clear that there is no benefit for you being in the US doing the work. What's possibly even more important is that you need to convince the border agent that you do not need a work permit to do what you are proposing. I think you are allowed to things like develop software, write a book, manage a foreign business, etc. But I'm not sure you are allowed to do things like ship goods you produce unless you are only shipping outside the US (if you are making something yourself and shipping it within the US, they might say that you are benefiting from being in the US to do your work and hence need a work permit), etc).
Getting entry into the US : As silly as it may sound, this can be tricky. As a Canadian, you are allowed to enter the US for up to 6 months as a tourist but border agents don't have to let you in that long. You need to convince the border agent that you can support yourself during your stay (without working illegally) and that you'll leave the US when you are supposed to. To do this, you need to maintain ties with Canada (home, job, etc) and it's subject to interpretation. On a related note, the US has a bizarre formula for determining if you are a US resident for tax purposes. If you spend 183 days or more in the US in a single year, they will consider you a US resident for tax purposes and you will likely have to file US tax returns on your world income. Furthermore, their calculation is actually # days in current year + (number of days previous year / 3) + (number of days of two years ago / 6). If that total is >= 183, you'll be considered a US resident for tax purposes (i.e. if you spend 5 months per year, every year (150+50+25), you will be considered a US tax resident. There are other rules regarding this so it's not quite black and white but it's certainly something to be aware of and plan appropriately.
FWIW, we've also considered of doing the same but it's not a good option for us.
Hope this helps,
Mike