I have just tested it for a few minutes.

What I really like is that it opens much faster than Excel and, as advertised, can handle large files. I will certainly consider buying it after the trial.

A couple of improvements that you could consider are: 1) implement row/col freezing like in Excel and not via split view because the split view is not as space-efficient (you see fewer rows on the screen), 2) add an option to add GS-Calc to "Open with" context menu, 3) a more modern UI.

Congratulations on shipping a very promising product!