Great free version, great pro version, great support

The free version worked for me on several sites. The free version’s great.

When a new designer called for something more I picked up the pro version, and liked it enough I bought the developer’s edition. The pro version’s even better.

When another designer needed something particularly cool-looking but complex for their own site, something that goes beyond the Pro version, the support folks really helped me out. So their support is great too.

If you’re going to have popups for more than simple nags for newsletter signups the Popup Builder plugin is an excellent choice.