Their $10 unlimited browsing plan is good (particularly when coupled with a port 80 VPN or proxy), but many US SIMs offer better rates in Canada than Canadian prepaids if you are not confining yourself to a particular market. Take a look at Telna's rates in Canada.

My wife and I split one contract Telus iPad SIM on their self-adjusting plan which goes from $6 a month to $35 a month. I pay $6 if I use less than 10 megs (e.g. don't visit Canada that month) up to $35 for 5 gigs. Typically my wife is in Canada one week a month and it is perfect for us.