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?

Not much faster if you only need a few symbols, and if you only work in one document. I used to make such tables for large documents before I created Mathpad.

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.