I have the 2015 MacBook Pro running now. It took a lot of iterating to get the right version of the OS running on the machine and to then restore a Time Machine backup on the machine without having one or more extra accounts on the machine. One thing I will never understand is why Macs are so slow at transferring stuff over a local wifi network. All the advice on the net says you need to use faster wifi, but my wifi is very fast. Here are speed test results communicating with a server in NYC, about 100 miles away. Why is it so much faster to communicate with that server than it is to communicate with a laptop that's in the same building?