Michael,

Yes, google base is essential and it can work VERY well if your descriptions and headers are done correctly, but you need a LOT of products in the feed for it to send decent traffic. Also, the really good thing about google base is it's conversions. The people that are using google base are already in a mindset to buy and I've found them to convert much better than most other forms of traffic. It's no good getting loads of traffic but no conversions,... for example:

Any traffic from a forum like this to a shop selling handbags is VERY unlikely to convert if at all, however if you have a site talking about marketing you stand a better chance.

So for instance if you get 10,000 visitors from a site like this to a handbag store it might only convert 0.01 percent of the time and result in 1 sale.

However if you get say only 20 visitors a day from google base but they convert at roughly 10-15%, then that equates to 2-3 sales per day. And that's why it's very important to have something like google analytics in place to track the effectiveness of all your traffic sources and then work out the value of each visit. Then concentrate on improving the traffic from each of these channels. Don't dismiss the others, I'm just saying prioritise your tasks. Also, being in google base means that your item will appear in the results ABOVE the normal searches in some cases. Also you have to make sure that you are targeting the right country. In the webmaster settings google.com/webmasters/ you set the location of your store to match customers local to your store (they tend to convert better) .

Regards,