Apphud takes away overhead handling and testing many edge cases within Apple and Google IAP systems. Blog posts, docs, and support are all outstanding. Also, there are many possible analytics integrations, but I haven't grasped that part yet.

As of me, the best thing about Apphud are their powerful SDKs with tons of handy methods of getting user subscription/auto-renewal state, getting iAP info etc. Especially, if your app is cross-platform, and you should keep in mind that you must provide the access to premium features on iOS even if a subscription was purchased on Android. Apphud solves this problem. And, finally, their support team respond blazing fast and APIs are really well documented.

Really easy to implement and great SDKs. AppsFlyer integration works like a charm. And amazing Customer support!