How much faster is Mathpad than creating a per-document table of symbols with their Unicode numbers and/or latex values and copy/pasting until you remember the Ctrl-Shift-u nnnn sequence?
Mathpad's killer feature is working anywhere you can type text, not only document editors. I've found it particularly useful when putting together technical presentations in Powerpoint, and when documenting the algorithms I write at work which are rather math and physics heavy.