This review read like an Apple user looking for things to whine about. I don't recall seeing anywhere in the verbiage of press over the last two days any promise from Amazon that it would be some universal media-seeking device.
That being said, like any respectable media streamer these days, it DOES support Plex access, which should be your go-to tool for local content access. If it's on the same LAN with a client, you can also connect to it via DLNA and thereby use it with pretty much set top box smart enough to connect to the internet.
The single best STB I've ever found in terms of capability is the LG Smart TV Upgrader, which LG sold for about two months back in 2009 or so. It supports SMB, AFP and NFS, but it also has support for Netflix, Youtube, Hulu Plus and Amazon. It can play h.264, open VideoTS folders and it doesn't have a problem with AC3 or DTS audio. Unfortunately, it's slow as hell and the UI is ugly. I'm not entirely sure if LG is still releasing firmware updates for them but they're a pretty good alternative to a fully functional HTPC.