From Google Blog:
Instant results in the “Shopping” view
Now you can shop faster than ever and get the speed of Google Instant when comparing prices, looking for nearby stores and learning about products you want to buy. For example, if you’re searching for a cast iron skillet, we’ll start showing you relevant pans as you type [cast iro…]. Click “Shopping” in the left-hand panel and try searching for [sweater wrap shawl], [android phone] or anything else.
Logical move by Google to apply the Instant Search concept on all its verticals, including Product Search. However, I’m not as convinced as for web search : the main drawback is speed… In my experience, the Shopping results take too much time to be displayed for Instant Search to be useful.
Also, the ability of Google Instant to bring back the advanced search queries I’ve done in the past (i.e: using the “site:” operator) but to not support those within Product Search (I’m therefore landing on no results pages…) is quite frustrating, almost upsetting…
Also to be noted that Google Instant is not available from the homepage of Google Product Search. It seems to me Google has rushed this development.
As side notes, while testing Google Instant, I’ve noticed two small changes that I’ve found pretty interesting: