It is another compliment to your existing AdSense ads. But the HP ads also count impressions, meaning that any traffic your hubs get has the potential to earn you money even the person does not click on the HP ads.
HubPages Ad Program was released to nine beta-testers in late February and after successful testing, it is available to all. From my 7 published hubs, I've earned more than half from HP ads in a week than from Adsense in over 3 months. So I think everybody should consider HP ads as it provides a consistent income on your hard work.