The problem I have is that vendors are essentially using the control they have over the operating system to limit competition in the media sales area. If Microsoft had done something like this, they would have been sued into oblivion. Apple is indeed the worst offender. The entire reason why there is no Vudu app for iOS and the reason why you cannot buy media via the Amazon iOS apps is that Apple demands 30% of all in-app sales. That makes it literally impossible for anyone to compete with iTunes when trying to sell media to iOS device users. I don't understand why the FCC is not taking a dim view of this, because it is flagrantly anti-competitive. I don't know what the deal with with Amazon, because they actually do allow a Vudu app on their tablets and the also-competing Flixster app on Fire TV. The issue there may be Vudu. I am not sure. Android TV is too immature to tell where the issue is, but I can get Flixster, Vudu, Amazon and other competing media outlets on my Android devices without any issue. Google sells media, but does not appear to abuse its control over the OS the way that Apple does.
Roku is, in my opinion, the best streaming platform because it does not sell media and is not part of any one media ecosystem. In fact, the only ecosystem not available via Roku is Apple's and that is Apple's choice. I have fully functional access to Vudu, Amazon Instant Video, Amazon Music, Google Play Video, Flixster, M-Go and any number of other content providers. Roku supports damned near every service out there and provides a very slick unified content search that works across all of the major services. The new version even adds voice search. You tell it what movie or show you want to watch and it lists every service that has it and how much it costs. I will take that over absolutely anything else on the market right now.