That's awesome.

I too had a similar experience in mid June on my ATL-BOM (Y was over sold) so they put me in business. I was on a Q fare outbound. On the return I was on a T fare but during ticketing it self - the agent gave me my business elite seat and a voucher for the lounge in BOM. I was pleasantly surprised and very thank full to the agents and Delta for the upgrade.
However, my ticket was not changed to Business Class so I did not get 1.5 times the mileage.
The ~16 flight each way was very comfortable this time around for sure.
Thanks Delta...