I am not aware of problems with Hipster but to be honest I do not use HD shutdown.
One thing you need to ensure is that there is no service accessing the disk regularly like a napp-it alert job or the Solaris fault management daemon fmd that you may need to disable
One thing you need to ensure is that there is no service accessing the disk regularly like a napp-it alert job or the Solaris fault management daemon fmd that you may need to disable