I've been looking to buy one of these Apps, but then stumbled onto this news. It seems these Apps are losing AC3 Audio support, one after the other. So far "GoodPlayer", "PowerPlayer" and "Buzz Player" have all lost this codec. Apparently the patent holder is asking for a lot of money, hence the removal.
See this link for more info.
So if you use any of these Apps, don't just hit the upgrade button!
Apps Which Lost AC-3 / E-AC-3 / TrueHD Audio Support:
-1080 MKV Player Pro
-Buzz Player HD
-HD Player Pro
-VM Player HD
Apps Which Have Been Removed From the App Store:
Apps that still support AC3: