For developers who are new to startapp. The below peace of information may be helpful: Since new sdk has been released (September 15th, 2013) to satisfied Google Ads Policy, thing has been changed in terms of Advertisement type, ECPM, Referral Program Policy. Because Startapp pay per download model, so with new sdk, revenue from download significantly decreased, but you can earn high profit with revenue from impressions.
The ECPM of Startapp is not stable as admob( in some days it may be very high, but may be Zero for some days, my highest ECPM record until now is 23$). So, the total revenues still as high as old Startapp SDK if your apps have good performance.
You must recognize one important thing: Until now, Startapp is little more intrusive than abmob, so your app's user with AVG installed in their phone may warning your app as: "Instrusive Adsware". Other anti-virus may not. It may little badly affected your app's rating, but not significant. In my case i notify my users before installing app about this, then everything is OK. Highly recommend using combination of ads types : Banner + Searchbox to get impressions bonus. If you are plan to integrate Startapp to your android app.
Integrating StartApp now, going with my referal:http://startapp.com/rftjqoh to get $15 when you first reach 1000 downloads, plus $15 when first reach 250,000 impressions.
To invest more about new sdk, visit: blog.startapp.com/announcing-suite-sdks/
To invest more about Referral Program , visit: developers.startapp.com/Referral/Terms.aspx