First, rest assured, I don't plan to abandon slimKEYS. I'll continue improving it, I'm its main customer!
The main reason to make slimKEYS free is to get some more satisfaction from it. I realized it wasn't the number of sales that was driving this satisfaction, but the number of users. Since both these numbers are low, to be honest, I've decided that in order to increase the number that does make sense, I had to ignore the other number.
I understand seeing something you paid for becoming free is a downer, and I intend to fully refund anyone who feel betrayed. A blog post is coming Tomorrow about this.
But now that it's free, I do hope slimKEYS users will continue to spread the word, so it becomes a successful product (under my definition of success! ;) ).
Thanks again for the very nice and stimulating comments.