As I indicated earlier, hopefully when it's all implemented and working properly it's going to be a very positive development. I don't have a lot of details on how it's worked in the United States, but I have seen the figure that 98% of people who have to get authorization to go to the United States are approved almost immediately. If you're not approved, you can at least discuss it with someone. That facilitates rapid clearance of the vast majority of individuals. As far as I can see, it would have a very positive effect on travel to Canada. There may be some people who just don't want to bother going through the process of getting the eTA. It can be done at the airport, but it's much faster if you do it online. Apparently, it won't take more than a few minutes. You can then print out the authorization and you're all set.
My guess is that it will facilitate rather than be an impediment. It might be an impediment for a few people who aren't online and then they have to do it at the airport, but on the whole, I think it will be a very positive development in terms of tourism to Canada, particularly from the United States.