I felt the same, but when I saw they offer an upgrade price (by bundling it with classic for a hefty discount) I decided it was worth supporting a good Mac app even if I rarely use it.
Oh, 50% discount. I might bite. Sad thing is they had no way to tell their app store customers about this (at least not the very infrequent users like me), and I had to find out from a random HN discussion.
And I only discovered it indirectly through Gruber: reading about ML Super Resolution on Daring Fireball intrigued me enough to go check out the price on Pro.
