I transited through Ottawa while travelling from London to Washington - a slightly unorthodox way of flying that route but there was an excellent deal on Air Canada! I found the airport to be clean efficient and easy to use. I had to go through Canadian immigration before going through US immigration in Canada (it's fairly standard of course to have US immigration desks in major Canadian airports). In both cases processing was quick and easy - the fastest US immigration queue I've ever had at any airport and certainly much much faster than I would have faced at Washington Dulles! I do wish that the food options were a little better airside for travellers to the US but they were functional. I did find the language politics in the airport entertaining but then I've lived in Brussels and have past experience of capital cities that try to balance two languages; an ability to speak French might help if you're addressed in that language first (which happened to me a couple of times) but I doubt monoglot English speakers would have a real problem.