Have you seen this page: https://support.busymac.com/tickets/10983 ?
You can still subscribe to calendars hosted on Google, but you can no longer publish calendars to Google. This means you cannot publish local calendars, iCloud calendars, or Exchange calendars to Google. If you are currently publishing local calendars to Google, you should host your calendars on Google and subscribe to them instead.
To answer your actual question, there are many facilities available in BusyCal which iCal lacks - sidebar, better ToDo handling, addition of images to events, use of different fonts... and no horrible faux-leather look.
I have seen that page, thank you! That being said, it confirms that I do understand correctly that it's now a one-way relationship between Google Calendars and BusyCal. I believe this was the case with iCal a few years back, which is why I switch to BusyCal in the first place. I enjoyed the two-way accessibility. Follow-up question...does iCal now support publishing to Google Calendars?
Thanks for providing some of the other BusyCal features. I guess it's subjective as to which ones a person may or may not consider useful. Like anything else really! Unfortunately, it seems as though my initial draw to BusyCal is now null and void.