Symantec Management Platform (Notification Server)

Does anyone know of an industry standard for software delivery success rates and the authoritative source for that?

100%, and me.

Are you looking for some published whitepaper? Ideally, I would think a minimum of 90% would be desired, but depending on the software, whether or not it's an upgrade or remove and replace, the target audience, etc.

I would look to someone like Forrester http://www.forrester.com/rb/research or Gartner http://www.gartner.com/it/prod.../research_services.jsp

These are typically pay for output services.

As Benjamin Disraeli is reputed to have said, there are Lies, Damn Lies, and Statistics.
Good luck in your quest - I have been looking for an industry standard IT environment for decades and have yet to find one.
Ratio of mobile PCs to desktops has a significant effect on statistics, as does the type of WAN that connects different offices, where large companies have multiple sites. Even the efficiency of the personnel department can figure in the results, as if they do not inform IT that users have left and their machines are no longer "in use", then these machines continue to figure in the stats. Equally, as machines are taken out of service or rebuilt, it can be some time before their 'retirement' or "change of identity" is noted in the statistics.
Clearly if you have 5 users in one office, you have a good chance of achieving 100% but if one user is on the road all the time, it will drop to 80%.
Jim may have his own experiences, but I've seldom seen corporate statistics that exceed the low 90's in percentage terms, and this is inevitably a combination of all the above factors.

Our goal is over 90%, then it's considered "successful"

For major updates, I'll run reports of machines missing the updates and send those to local support personnel to address.