Note that you only get one coffee per car if you are ordering through the drive through. I agree with the others that I prefer McD coffee to Tims. If the kids didn't like Tims donuts so much, we'll probably get our coffee fix at McDs.
I don't think McDs coffees are all that popular at least based on a couple of observations near our home where a Tims and McDs are next door to each other. McDs has a big poster offering free small coffee but the queues at the Tims' drive through are always much much longer (at least during breakfast and in the evening).