I've been using DNS Enabler for over 4 years and can testify that it's rock solid. While you can find many references for configuring BIND, your actual requirements will always differ from those of the providers of the information. Thus, customization is extremely difficult and requires trial and error. DNS Enabler completely simplifies the process and allows ongoing edits with ease. For those who are complaining about the lack of a true demo, any savvy user could copy the BIND configuration files during the demo period - thus eliminating the need to purchase a license. For $15, the developer more than deserves to recoup some of his developments costs. If your network would benefit from managed DNS, this will be the best $15 bucks you've spent in a long time. Heck, if the developer comes here, I'll treat 'em to dinner and a few beers, too ;-)

By not providing a demo version the author is unfortunately, shooting himself in both feet

Requires a serial number to run. There is no demo mode or demo serial number, therefore "buy before you try."