This is not a formal case study and sorry but I am not about to expose confidential details about my clients. This is a theoretical Google Panda recovery plan for product pages. Feel free to critique it and share your smarter ideas. If you want to waste time complaining about Google then skip this thread and visit your local bar. This thread is about discussing productive methods for addressing Panda product pages.
Before we begin let's admit that some webmasters aren't smart enough and/or didn't save any money and/or are too lazy and/or aren't creative enough - these people have very little chance of recovering from Panda. Many of the things I am about to mention are not easy. I know this but remember you aren't lazy either. Ok so let's assume you are smart enough, have a good amount of cash to invest in your site and are ready to work hard to implement your creative solutions - Let's Begin!
For this theoretical Panda site recovery let's say you have a 10 year old domain with 3,000 pages:
1,000 product pages
1,000 blog pages
Dealing With Your Panda Product Pages
Ask yourself what is the value of each product page? Be honest about the value proposition that you offer. Unless you have a crazy patent and are the only person selling a great must-need product then you need to develop unique value for each product page. Look at your top 10 competitors and see what they offer on their product pages. Then head over to Amazon and other huge e-commerce sites and look at what they do on product pages. Now create a list of all these features and value adding bits of information that your consumers are being offered elsewhere. You want to at least match these features if not surpass it with your own new value to set yourself above the competition.
Ensure each product page is significantly unique
Many websites have a product page for every item they sell. You should not do this. If the products are 99% identical DO NOT CREATE SEPARATE PAGES. If you sell the same pencil in a 10 inch length and a 12 inch length, combine those product pages and use a drop down for the user to select the length. If you have created multiple pages for each individual product (like a product description page, stock availability page, etc.) combine the information from these weak & anemic pages into one strong & informative page.
Write a unique description for each product
Now that we have condensed the huge pile of product pages into unique products it is time to write an informative description for each page. I am not talking 50 words. I am talking a few hundred words MINIMUM. Consider using a paid service like mturk to help you automate the process.
Delete all garbage from the product page template
Do you have banner ads that generate almost no clicks? Remove them. Do you have redundant links? Reduce them. Use a heatmap service to determine what is used (or worse what is creating a usability roadblock) and deal with it. Anything that can distract the user from noticing your valuable content needs to be reviewed and likely removed. You want as much of your unique value to appear above the fold. Is your page header too large? Shrink it. Think about how this page will display on mobile devices. Even if it is displayed on a big desktop screen, consumers attention span keep shrinking so you need to get rid of any and all template garbage so your shiny valuable content is super easy to notice.
Add even more useful content
Go back to that research your did on your competition and make sure you are providing better content than all of them combined. I am not talking about 100 words. I am talking about 600 words MINIMUM. Personally I target a much minimum for my pages. I am not talking about fluff or non-useful filler. I am talking about adding helpful, high quality information that is written in a clear and easy to digest manner. Use real paragraphs or a list of detailed bullet points. For example you can include some paragraphs for suggested uses, care & maintenance tips, DIY projects, etc. If a user ever emailed you a question about the product, include the question and your lengthy answer on the product page. Get creative.
Deal with customer reviews
Institute a 100 word minimum on your customer reviews and enforce basic grammar and spelling. It isn't helpful to anyone to have a review like "dis produxt is badd" even if the product is bad. It is much more helpful for your SEO and for your visitors to have a review that explains why it is bad. Consider offering rewards for reviews or giving away free samples in exchange for substantial & informative reviews. User generated content needs to be monitored and handled properly.
Consider even extreme ideas
If your product pages have never ranked well and historically have never been good performing landing pages then consider an extreme idea like noindexing your product pages. If 99% of your customers enter your site via the homepage or your blog then removing these weak product pages from Google's index won't significantly decrease traffic and can help greatly improve the overall health of the website.
The end result for the product pages is to have an abundance of value that is not easily found on any other website presented in a very noticeable and easy to digest manner.
This is just a starting point for recovery.
Please share how you would address product pages impacted by Google's Panda :)