OK, old wives tales told by old wives again...
Running YOUR site under SSL hasn't got anything to do with GOOGLE returning referral data because THEY run things under SLL. Apples, oranges, blah.
The implications are the HTTP and HTTPS server on your site are treated as two completely different domains in Google, just like www and non-www. Therefore, running a site with half the content in HTTP and half in HTTPS will probably dilute your site ranking and most likely anything in the HTTPS side will have a touch time ranking being that far down the PR chain of your site in the first place.
Not to mention if these products are behind a login then you need to allow crawlers to get past the login in order to crawl.
Your SSL pages will load slower by definition because SSL adds time, therefore Google will probably rate them as slow loading pages unless they give you an adjustment for being on SSL which I doubt.
The customer experience will be excrutiatingly slow, like it is with a bank's website, and shoppers may bail because of the slow experience.
If the only reason you're putting it in SSL is because of the login, that's silly. Make the login SSL and once secured redirect back to those pages. Having pages only available to people that have a login doesn't mean they have to be displayed in SSL to be secure. Your server is tracking a session that knows the person has logged in and the pages, unless containing secure data, can be run though the HTTP server just fine until checkout.