Although dynamic arrays are good in principle, the current implementation has two features that cause significant problems for current users of array functions.
1. I use UDFs returning arrays extensively. Often I only need the top left value, or some part of the return array. If the whole array overlaps some existing data, these functions now return SPILL.
2. It seems that sometimes the new Single function is applied automatically. Presumably this is not compatible with earlier Excel versions.
Rather than deprecating use of Ctrl-Shift-Enter, why not incorporate it in the new functionality? I suggest:
1. If the function is entered with the Enter key, it will return the entire array, or SPILL, i.e. as in the current version.
2. If it is entered with Ctrl-Shift-Enter it will return a single cell, or whatever range is selected (or SPILL if the selected range contains any data).
3. Allow the returned range size to be reduced in extent, as well as increased, when entering with Ctrl-Shift-Enter.
4. Allow conversion between the two behaviours by re-entering with Enter or Ctrl-Shift-Enter.