Re: Life and shift
I'm aware of three or four migrations to the latest version of SAP (which includes) HANA and they all went well. The first one is over a year old and the customer is still very happy. I can't claim much credit for the success as I mostly only got involved in arranging hardware.
The key to getting it right seems to be to follow SAP advice with customisations/APIs.
As for going to the cloud... hmmm, a topic for another day perhaps :-)