"when the site launched the copy was unique and the most comprehensive under the one subject available at the time."
I have a site which was full of comprehensive texts about widgets (researched dozen of manuals, pdfs etc, in order to add value and be more comprehensive when compared to competition) and was badly penalized in February.
However, the posts were maybe the best when it comes to details included in the product descriptions, but there were a couple of things missing:
- original images
- personal opinion about a product
These were missing since I hadn't got hands on the product, but used manufacturer's site to get details and images.
So I decided to go the the trade show and get hands-on new products.
Posted a review of a product with original images on the penalized/pandalized site and got ranked between #130 and #140 on Google, but #1 on Bing.
Posted a review of another product also with original images on a brand new site (no product keywords in the domain name, almost no inbound links) and got ranked between #7 and #14.
Repeated posting of similar reviews of other products on the penalized and the new site and got similar results.
So, on the one hand, I think you have to get hands-on the product you are writing about. But, on the other side, if you post these hands-on articles on a penalized site, expect to see all kinds of nonsense pages ranking above you and you will be nowhere.