8 hours is way over the top, take a look through the errorlog to see which parts took so long. I am not aware of any OS dependencies or bugs that affect this so reporting to MS is probably worthwhile.

If you have a lot of databases that definitely affects the time this takes to run (though I have a server with over 300 and the script upgrade phase was still just a few minutes).

Only other thing I can think of is the database log files having large no of VLFs affecting database recovery time. How long does a node usually take to start up?