Why am I getting only 2000 rows using Analytics REST API Synchronous report run

Ok I got it after reading the release notes. http://developer.force.com/releases/release/Winter14/AnalyticsAPI

You can only get up to 2000 records using this API. What's the use of an API that doesn't give me all the data, I don't know. And they could have stated it in the developer docs. Wasted 2 days on that.

You are missing the parameter "allData": true,

This boolean flag specifies how many records are returned. The quoted document (page 39) mentions clearly

When True, all report results are returned. When False, detailed data for the first 2000 report rows are returned.