I've also got an LTF upgrade to Regallia gold from my Millenia LTF but I also feel that it's more of a downgrade (at least for me). I do not visit airports so lounge access isn't really valuable to me. Shopping/Food/Utilities are taken care by 5% Millenia cashback so I don't see any good incentive to move to Regallia gold.
I decided to upgrade as I was not getting any significant benefit out of Millennia.
I will tell you how-
Millenia gives 5% cashpoints on 10 specific merchants out of which I use Amazon, Flipkart, Myntra, Swiggy, Zomato and Tata Cliq(occasionally) only.
Millennia gives 1% on all other including EMI and Wallet trx.
For Amazon - I have ICICI Amazon
Swiggy/Zomato/Utilities - I have Airtel Axis
Flipkart/Myntra - I...