It's a yes and no thing depending on the rider as to where they travel to/from where they live. For me, I am a 15 minute walk from a Hurontario transit stop today + X time for a wait for one of 2 buses on it + 5-7 minute ride + 10 minute walk to GO Cooksville Platform + X wait time + 25 minute train ride to Union or about 10 minutes to Kipling + 5-7 minute walk to the subway = 45-49 minutes + wait time to Kipling and 60-62 minutes to Union + wait time; then another 10-15 minute walk to where I am going. Taking transit its 8 minutes to my bus stop + 2-3 minute wait + 25 minutes to Dundas stop for Kipling + 10 minute walk to the subway or GO Platform + 25 minute trip to Yonge + 5 minutes for a Yonge subway + 10-15 Minutes to King + 6 minute to where I am going = 85-90 minutes. Other than the Yonge line I have a seat compare to standing for 25 minutes on GO. Sometime I can get a seat on the Yonge line going in and have a seat all the way home. A number of times I am going to X in Toronto and that rule GO out right from the word travel. There are times I been able to get to Metrolinx office in 1:15 minute by local transit.
If we look at a rider near the Dixie they have a 10 minute walk from Dundas + X time to get there and about 20 minute GO ride to Union + wait time for the train compare to a 10-15 minute bus ride + 60 minute to Union + walk time to Dundas.
Where it become better to use GO is from Erindale to Lisgar than try using the 109 express bus from Islington/Kipling.
If all day service happen for every 15 minutes, you may see more station to station in Mississauga travel as well to Kipling west of Cooksville.
As long people keep on being Union Focus as where everyone is supposed to go, they are missing the big picture where people are really traveling to/from in Toronto. Downtown Toronto is not the centre of Toronto today like it was 10-30 years ago.
For me it's more like Yonge/Eglinton, Kennedy and a few other location outside normal weekday travel. Even my normal work day travel this year is been off the wall as it been all over the place.