Google no longer all gooey over price comparison sites?

Price comparison is quite difficult to implement on small-time affiliate sites without paying for an expensive aggregation service. But Google frequently cites price comparison as one of their examples of "value" provided by a site.

I am working on a pseudo-comparison shopping solution that would be accessible to small affiliate sites, and I know price comparison widgets convert very well regardless of their SEO value, but just wondering what your take is on full-on comparison sites and whether that is a viable model any more?

I can say that when I used to try to send Adwords traffic to affiliate bridge pages (not a viable model these days, not sure it ever was) I used to get landing pages rejected with a message along the lines of "comparison shopping pages must have 3 or more different retailers listed". Wish I could find that email, I can already see people disbelieving that, but there is something along those lines in the Adwords help, though more general:

So the Google Monster generally likes price comparison and that is something that is fairly easy to find algorithmically.

And besides Adwords, time was that every product search would throw up results from PriceGrabber, Shopping.com, Shopzilla etc. But I am just not seeing them in the SERPS now - it's all Amazon and eBay (which are basically comparison engines anyway due to the large number of retailers selling through them now) and the top review sites (CNET etc.)

A lot of comparison shopping sites are very thin and have huge duplicate content issues, but still, they do provide value of sorts. So has Google got a downer on them, too, now?