The goal of this article was certainly not to say that there is one right answer. Unfortunately, the issue is not that simple. The biggest question is what will benefit your customers the most. If you have a large existing customer base, Tiger is probably better for you for now.
If you have no customer base and are targeting early adopters, Leopard offers sufficient developer incentives to dive right in.
One thing to keep in mind at the end of the day: If you want people to purchase your software, then you want to target people who show a habit of buying new software. Coincidentally, they are the same people who purchase new operating systems fairly early and keep up to date on their hardware.
If you are targeting people who have not upgraded their hardware in five years and have not purchased a new operating system in four years, you might want to reconsider.