Personally I have found pretty good results with the product extensions but you may want to also check out AdWords product listings (different from extensions). With Product Listings you create a new campaign and the ads appear as an image with pricing vs image/pricing as an extension to your text ad.
I have seen cases where the wrong products were pulled from the Merchant Center feed for the extension or listings so consider adding some attributes to your MC feed for 'adwords labels' and 'adwords grouping' and then you can set filters on your product extensions and listing to make sure you have the right products served for a particular search query. Here is a adwords help center link with some details on the labels and grouping attributes.
LOL I hear you setting up the feed with AdWords can be a little tricky to get just right.
You might be able to save yourself sometime if you set a filter (have you noticed the filters?) - you don't necessarily have to add the AdWords attributes to your feed you can also filter on other feed attributes - here is the list of attributes you can set filters on:
product type brand condition adwords labels adwords grouping
You will not see the filter option on an already created extension. You only see it when you create a new extension.