Mine went trip went fairly well yesterday. A couple of comments for others reading this thread
1) My inbound flight was rescheduled 90 minutes later than when I booked it and I eventually got in 1 hour later than originally planned at 8.45am. Turns out migration is mayhem at this time and I coincided with inbound flights of all the US legacy carriers and an Alitalia widebody. I thought at times I was not going to make it. Took an hour to clear immigration. If like me you are flying in with the intention of going straight to the bus terminal, bear in mind it could be cutting it a bit fine. My bus was at midday
2) I bought my ticket via one of the websites references on the first page. My ticket said that I was going on El Rapido. I went to the El Rapido kiosk and they told me that my trip was operated by Andesmar. So factor in some time to work out which operator is taking you. Seems there are the bus equivalent of code shares
3) Border immigration was quick, about 45 minutes for everyone to file through, a nice chance to stretch your legs
4) Have some 100 CLP coins with you because you get asked for tips thrice. Once after they board your suitcases, once when you take them off at the end, and in the middle the driver came around with a paper cup for tips for the guys taking the luggage off at customs
5) As a data point, my trip also too 6 hours 30 minutes
Does anyone know what that train track is for on the Argentina side? Seems to run from the tunnel near the border to when the Andes peter out. Looks quite elaborate with its bridges, tunnels and corrugated cover in parts. Also looks to be out of service as the tracks are covered in rocks and plants