Thanks all for the useful help.

The Grab app was very good, once properly installed and activated, which was a royal PITA. During a major downpour, rides were hard to get and prices went way up. Otherwise it was fine. MRT doesn't take AX, but worked fine with our MC and VI. I still don't know how much the rides are, because I had one 7¢ pending charge show for probably a dozen rides over 4 days, and nothing has yet posted as final. Took a taxi from the airport, and a premium Grab back to the airport. The airport wasn't as impressive as I had expected, but it was a pleasant place. The SQ Business lounge did have a quite appealing spread of F&B. I can't say that I've ever had laksa along with XO cognac at the same time anywhere else