I've been looking for good data on iOS and Android apps. Can anyone confirm that Xyologic is a solid source of data and that the estimates are reasonably accurate? Is there a better source of download data? (appdata.com is good for usage data).

Haven't examined Xyologic. I tend to follow Flurry's announcements as they've had good adoption from reputable developers. Though this tactic only illuminates larger trends (app category usage).

For more fine tuned tracking, I track unique URL formats on Twitter to act as a proxy for usage and sharing. I'll capture tweets with specific URLs (like Instagram, Spotify, Photoset, etc) with Datasift for a day or week then calculate a rate of sharing.

It's a pretty tricky task, as no one has a clear picture besides the OS makers. Until an Alexa/Quantcast equivalent emerges I'm not sure it's worth the effort.

Drew, how do Xyologic and similars create their estimates? I understand how Flurry, Appannie, Localytics create theirs, but what about the third-party estimates?

No clue. But their About page is worryingly vague:

"Using a series of breakthrough inventions, Xyologic is pioneering new ways in app search for users to explore the mobile app world, through intuitive suggestions and more specialized app genres."

'Breakthrough inventions?' That's almost as worrying as 'Patent Pending'.

Would love to learn more and find out I'm wrong, but their site isn't very helpful.

xyologic.com

It seems roughly accurate for a demo app I published years ago. But without verification from a few large apps comparing their numbers to Xylogic's, I'd take it with a grain of salt.

xyologic.com

Though it categorizes my app as "Relaxation Sounds." Whoops!