Just a disclaimer, I am biased towards public transit as a sustainable way for York region to grow. Alright that being said time to dive in!!
YRT is a much loved or hated service depending on who you ask. Having public transit automatically elevates York region as a growing area so gotta love that. Having public transit which is less technologically accessible than GRT (shout out to UW and WLU students) a big negative. Still waiting on the TTC and YRT to rollout widespread and effective text support for bus times.
If you are using the major routes such as the 91 and 99 (VIVA is a unique system) you'll find that the YRT is quite frequent and for the most part reliable. However most of the other route suffer from the curse of the suburbs and as a result are infrequent and compete without success with the plethora of cars on the road.
Their recent strike was a huge setback, less so for the heavily serviced routes of the 91, 99, and a few others (sensing a theme?). The nearly two months of free transit is a step in the right direction in terms of gaining back users and I have noticed that the number of users is back up to pre-strike levels (non-scientific and statistically unusable of course =P). It has made me consider taking public transit over getting a ride from friend or my parents, so clearly the free transit has been successful in converting me.
The objective of running a public service is to increase the level of community uptake. YRT has done an admirable job considering that it must run through a heavily auto dependent series of towns. I feel that those who complain about the running of the YRT (myself included) need to rethink how public transit is supposed to function (think London or any Asian Metropolis).