In case someone reads this article in the future, SQL Server 2008 R2 on Windows Server 2008 R2 Enterprise (upgraded in-place) can and does use 64 GB RAM. Windows was patched last week and rebooted. After reboot,

select counter_name, cntr_value
from master..sysperfinfo
where [object_name]='SQLServer:Buffer Manager'
and counter_name in ('Total pages','Target pages')

Result:

counter_name cntr_value
Total pages 7077888 <--54 GB
Target pages 7077888 <--54 GB

In case someone reads this article in the future, SQL Server 2008 R2 on Windows Server 2008 R2 Enterprise (upgraded in-place) can and does use 64 GB RAM. Windows was patched last week and rebooted. 

After reboot:

select counter_name, cntr_value<br>
from master..sysperfinfo<br>
where [object_name]='SQLServer:Buffer Manager'<br>
and counter_name in ('Total pages','Target pages')

Result:

counter_name      cntr_value<br>
Total pages          7077888    <--54 GB
Target pages         7077888    <--54 GB