Seems to work a lot better than google play's search, which returns absolutely awful results. Searching for New York travel guide in google play will return travel guides for Paris, Rome etc...
Sadly it just seems to be aggregating a number of spammy download sites. Searching in my product category turns up pages on CNet, Brothersoft, etc but no original developer sites.
11,100,000 results for "twitter" now that is scary.
The idea is good but having application aggregators such as download.cnet.com, softpedia.com and others in the result means a lot of duplicate entries.
This will be handy for https://starthq.com - a web app directory I launched the other week.
One piece of feedback I've received is that people prefer to use a native mobile app if one is available, so the plan is to include links to app stores on the app pages. Unfortunately, none of the app stores offer APIs for retrieving apps based on keywords.
From what I understand with Apple you need to specify the country in which you're searching and you may get different results for the same query based on that. There isn't a way to get back a single link to which you could redirect all users that want to download the iOS app, regardless of where they are from.
Edit: so yes, I was wrong to say "none", but Apple has its own set of issues making it difficult to do