I downloaded this out of curiosity, and found it to be quite an amusing app.

It's premise is to simply provide the player(s) with a playing table, and two decks of cards. The rest is up to you.

One thing that would have made this even more fun, (for me) would have been some kind of scripting language, to allow custom scoring. Also, being able to draw cards from a deck in an easier fashion, than what is provided, would also be welcome.

But on balance, the tools that are provided, are adequate for playing alone, or against other players. (As long as someone knows how the scoring is supposed to work.)

In any case, the opportunity is there to make a 'Solitaire Maker' application, where people can build their own solitaire games. Particularly if scoring and such could be taken care of by the computer.