Open Source NMS Software

I'm looking at depolying an open source-based NMS solution, and I'm looking at a couple products, mostly OpenNMS (http://www.opennms.org) and Zenoss (http://www.zenoss.org). I like the looks of Zenoss, but I've never really heard of it and I'm wondering if anyone has any experiences with it that they can share before I go and spend hours on an install/configuration. Is there something wrong with it, and that's why I've never heard of anyone using it? Am I just out of the loop? Even better would be someone who's used both products and could give me a quick comparison. I'd also welcome suggestions of another product (as long as it's not bb, nagios, or hobbit) that I should be looking at. Thanks, Gary Giesen