Leadbolt - still using?

Hi there!

I heard that LeadBolt was really good about a year ago. Anyone using it nowadays?
I implemented it in my Android and iOS application. I am wondering if there might be a problem with their ad campaigns, because I am showing ads all the time at the bottom, refresh rate is 120 seconds. First day I got 147 impressions, which seemed to be kinda normal as the app was not downloaded so many times, however, yesterday I got more than 300 downloads (mostly from China and Taiwan), but only 21 impressions. Are the users using app without wifi/internet connection and banners does not show up, or is this a problem with their fill rate or whatever?
Is that normal? Could you please share your experience if you are using LeadBolt ad network.
Currently I am thinking to switch to RevMob. Is this network any better from your experience?

How did you find out that you had downloads from China? Google Play is not available in China.

Do you see requests in Leadbolt, but a low number of impressions?

I was referring to iOS downloads (where I can see countries from which app was downloaded), because the difference between impressions and downloads was huge. Android version had very few downloads, so I thought that number of impressions might be right.
LeadBolt does not show the number of requests, but as I am using HTML ads, I decided to check the number of HTML page visits in my server and… 693 requests… and only 21 impressions for iOS version and 175 requests for Android version with 55 impressions. There must be something wrong…