When I run Export-DMVInformation -instance 'my2008R2server', it gets to Query 42 (IO Stats By File), and then runs into an error after about a dozen databases Incorrect syntax near ')', which I could re-pro manually doing Glenn Berry's script in SSMS on the last database it hits, which told me it's not an issue with PowerShell but with Glenn's script. I realized that this particular database is at a lower compatibility level (SQL 2000, compat level 80) so Glenn's script throws an error since it's not for a SQL 2000 database.
So I then tried doing Export-DMVInformation -instance 'my2008R2server' -excludedb 'mycompat80db', and the PowerShell script stops at Query 40 (Ad hoc Queries), and doesn't go to Query 41 and above.
Hence, the bug seems to be when using -excludedb, it does not go beyond Query 40.