Having lived in Canada for about 8 years (I came here as a Master's student in 2005) I can share a few things that the posters above haven't gone deep into. I'll leave out some areas that I'm not well versed in/others could add.
THE BAD
The weather was mentioned briefly above and I think this is a sticking point for many like myself.
1. Sports:
I consider myself very sporty and love to play all kinds of games. Coming from India, I miss playing cricket the most. But I love Basket Ball, Tennis, Football (soccer!) and everything played outdoors. And in Canada you're most likely to find yourself to be unable to play anything for a good 6-9 months depending on where you live.
2. These are some of what the locals would say: "You can play them indoors" -- comes with a heavy price tag. "You can learn how to play winter sports like hockey" -- comes with a heavy price tag (because of the gear) and often you're too old to learn new tricks, especially on ice.
3. Commute:
Public transport here isn't that bad (in Toronto, at least), but it's mostly because I'm use to the way things work here. Weather could wreak havoc on your commutes more often than you'd like. You could get find yourself stranded in airports and train stations during holiday seasons (in December, when the snow is at its worst). Cannot bike for more than 4 months (even though, personally, I bike throughout the year).
4. Clothing:
You have to wear multiple layers of clothing just to take your dog out to pee. Getting out of and entering the house is a process. Coming from India, I just couldn't get used it, even after 8 years. You cannot just walk out with your shorts and sandals for more than half the year.
Bottom line: this is not a good country for outdoorsy people. But also be aware that this is not a Canada specific problem. Close to half of the United States shares these very problems (including cities like NYC). My girlfriend and I have been seriously contemplating whether to move to one of the southern states (like California) or to Australia. We'll probably choose California because it's just closer to where we are used to being.
Weather is number 1 sticking point, now I'll make brief points about other things:
Education: Good.
It has fairly well funded university system. One of the best countries to come in as a student.
Infrastructure: meh.
Half decent roads, decent highways. Poor/expensive railway system.
Really good parks in all cities with special attention to various needs -- dogs, children, elderly, families etc.
Communication systems: used to be terrible/expensive because of big corporate monopolies. Now, people have better cellphone and internet options than 5 years ago (Wind, Mobilicity, Teksavvy are new alternatives). Things are getting better but nowhere near where the US is. For example: Netflix Canada offers 10% of all programming available to the US customers.
Politics: Not a big fan of the Conservative government but you can mostly turn away from politics (even in a city where Rob Ford is the mayor). Canada is mostly politically docile because it's a small player globally. They'd like to think otherwise, but they are not. They live in the shadows of the big(ger) brother US. Now, this is a a good thing, in my opinion. In fact, one of the reasons we don't want to go south is because we can't stand all that self-serving, self-important political climate of the US. And it's a generally liberal government even with the conservatives governing.
Food and prices: Again, things aren't as cheap as they are in the US, but it's ok. Food related regulations are slightly better here, so I'm glad to pay the extra price even if it's only slightly better than what's in the US. Tropical fruits and vegetable fluctuate the most in price (that includes tomatoes too). Local/organic option is limited for most of the year as nothing grows locally for most of the year. Varied immigration has meant that you get to eat all kinds of foods here, though.
Other goods: They are more expensive than they are in the US and you pay 13% HST on top. Now, exactly where the tax money is going is anybody's guess (not for daycare or the healthcare, for sure). Plus, you don't get as much variety because sellers don't bother with a small market that is spread so wide across. But I think it's still better than Australia given where it is (or not, it is really close to China -- what's better? being close to the US or China? I don't know).
People: this is a still a white majority country. But people of colour are also in equal measure in big cities. Now, does that matter? Depends. Having been in big and small cities in Canada I've had my share of racist encounters. But nothing violent or hard to ignore. They are generally nice and easy to work with. As is the common perception among immigrants, their niceness isn't always genuine, but it truly doesn't matter. Because, when someone holds the door for you, it doesn't matter whether they did it because they wanted to or they thought they ought to. I'd take the fake open door than a door left to close in all honesty. Some of the things I've read about Australia are quite startling in comparison.
That's my general take on Canada.
Aside:
To the person who chided Canada for being 'soft': It's outrageous that people can be so openly ignorant/bigoted. This land, the land that is now called Canada was 'occupied' by wanderers from east Asia about 15000 thousand years ago. As late as the 15h century there were at least 2 million of their descendants. Then came the Europeans, wiped big chunks of the hosts and called this place theirs. And they closed the doors to the remaining people. The people were born here since then didn't 'earn' their citizenship. It's ridiculous to expect, at least in principle, that one has to earn it. Why? (I know this last point alone will invite a whole lot of counter-punches, I won't be replying to any of those.)