So earlier in the year, i signed up with vserv, after a friend alerted me to their ridiculously high eCPMs ($5) and ease of integration (You just point their app wrapper to your apk, and it produces the final apk, integrated with their sdk).

Initially, their eCPM's were averaging $2 - $7, for about 2 weeks, and then all of a sudden they dropped to $0.1 - $0.7 (for full screen Entry & exit ads!) and stayed within this range for the next 1 month. Some days i was even getting $0.09, for FULL SCREEN ADS! Needless to say, i removed their sdk from all my apps, and replaced with the Airpush one (Am now averaging $1.5-$3 using their smartwall format) and waited for the Net-60 period (WHY???) to get what i had earned from vserv. 3 months later, they hadn't paid, and on contacting them, they apologized profusely and promised they'd pay up within 7 days. Well, 7 days passed without a word from them, and they have never replied to any of the emails i've been sending them.

Long story short, stay away from VSERV. They will scam you, give you embarrassingly low eCPMs and they won't even pay you whatever little you make.

On another related note, i want to try either StartApp or Mobilecore and would appreciate any feedback on their services. I've heard they have pretty decent PPD/eCPM rates.