I have been using VIVA, Express Route and Regular Service operated by YRT over the years.
I usually drive if I travel in my immediate neighbourhood as I don't think it worth for short distance travel for $4. But it becomes quite a deal if I am going to Vaughan Mills/Wonderland, Express to Finch Station and back during rush hours or as a connection for Go Bus.
Using Presto Card enable you to transfer to and from Go Bus Station for 75 cents.
Most of the time my bus arrives on time. But sadly, there is not frequent enough as the ridership is quite low.
Hopefully with the growing population in York Region, that will be improved over time.