The fact that you need a Canadian presence to own a .ca limits the potential market. That being said, trust and acceptance of .ca within Canada is really good, and imho CIRA do a great job of promoting the extension (well pretty great). It had among the highest growth of major cc extensions last couple of years.
You need to find a way to effectively market to Canadians though (and anti-spam legislation limit outbound). Probably very roughly a good .ca goes for a bit less than a comparable .com, but there are some much more expert than I over at the thread. I only hold about a dozen (among a 240 domain portfolio).