A quick note here after the past 4 hours of fighting with NFS on OpenSolaris 2008.11. If you are attempting to do an mount and get a Permission Denied from either Linux or ESX the solution is rather easy.
Make sure that the IP address that you are connecting with has a reverse DNS entry with a hostname.
That's it. 4 hours and that's the gotcha. If you don't have a reverse DNS you'll never get the mount to work.