On May 3rd and June 6th, Google introduced 2 changes to the required attributes for all products submitted to the Product Search feed. Neither of these changes require any code modifications to the existing AspDotNetStorefront feed format, however some additional setup may be required for some customers on both the storefront end and in your Google Product Search account.
Unique Product IDs
The first requirement is that every product have at least one unique identifier. Google's documentation here explains what acceptable identifiers are. The AspDotNetStorefront software adds Brand (what we call Manufacturers) and Manufacturer Part Numbers to the feed if that data is populated for all of your products, so as long as all of that data is filled out for your products, this requirement will be met. The link above provides information on locating unique identifiers for your products if you do not have that information available, and for requesting an exemption if your products do not have global unique IDs (in the case of home-made or unique products).
Tax & Shipping
The 2nd change from Google is more complicated, and can require a good bit of setup on the Google Product Search account depending on your shipping/tax schemes. Google now requires that they be able to give a customer an estimate of the tax & shipping for products based on the customer's location. More details
here.
To set this up, you will need to log into your Google Product Search account and go to Tax and Shipping. Here, you can enter flat tax rates, regional rates, etc. You can also enter either flat shipping rates, create a shipping table, or request that Google get live rates from UPS or FedEx. Note that the rates returned by Google will usually vary slightly from the rates customers will actually end up paying on your site