Josh Asbury:
I tried using OFBiz about a year and a half ago but found that it wasn't ready for primetime. I haven't looked back, so maybe it has improved since then.
I am partial to OSCommerce as a full-featured store -- if you are going to host it yourself. If you're not, then ProStores are the way to go. They let you take advantage of the power of EBay and provide embeddable widgets that allow for easy integration into Liferay. Since I'm no store expert, I tend to direct customers in that direction -- and everyone has been happy so far.
OSCommerce is a fine PHP store, AFAIK. Another cool PHP store is Magento. Right now Magento seems to be winning.
However, we're a JAVA shop. I don't have PHP programmers, and don't want to have more platforms to support. We're running one PHP app -- OpenX, but we run that one unmodified. We need to deeply integrate the store into the site.
I'm still looking, but OFBIZ seems like one of the best JAVA based stores out there. It's big and complicated and a bit of a pain, but it does just about everything. It's used for a bunch of commercial sites, so it's ready for prime time, at least with work.
