According to the LabVIEW Object-Oriented Programming FAQ, LVOOP is fully supported by LabVIEW Real-Time 2009 and greater. A quick search of the bug report database shows very few documented issues with OOP on RT, so I wouldn't worry much about uncited performance claims.
More anecdotally, a few months back, I used LVOOP to develop a large distributed application on Windows, and was able to port it to both VxWorks & NI ETS style RT controllers quickly and without issue. Even running on very old cRIO's (9002's), I didn't have any issues with memory or bugs (CPU on the 9002 was another issue ).
I hope this helps,
