IMHO, after letting this digest, I am not surprised by the decision. For one thing, Pope B16 is in his 80’s and from my experience with dealing with an aging mother who is a few years up from him, you count it a blessing just to be alive each day. Also the duties of being Pope must have taken its toll and who knows if he does have health issues to contend with.
May God Bless and be with Pope B16 and the Pope who will come after him.
Perhaps Benedict saw what went on when JPII was so frail and decided to humbly spare the Church that vulnerability. He was a close witness as JPII struggled at the end and he may feel a Pope needs to be at his most powerful to grapple with the snares the devil has set for the Church.
I see it as a humble decision. He knows it will be dissected by many unkind and uninformed hearts.