If the people doing this are listening: I don't think the business model is ok. If this keyboard is to get some traction, it will require us users to use it for real before paying. You can't have a keyboard lite, it's a vital utility, not a game. If I type a url or a password and discover that a character is only on premium, I'll switch back to my usual keyboard and not look back.

Another remark: typing number is very important and must be safe and fast, I didn't see a number mode. It should be easily done on five tiles.