Just bought the app. Few observations for the dev:
1. "playback" is spelled as "palyback" in the history page
2. I have 4000+ MP3s on my SD Card, there is no way to sift through them or even search
3. As others have mentioned, dumping music files with videos in a single, un-searchable list is a mess
4. The app is unresponsive during startup when it parses through all the video in the phone+SD Card
5. Performance is slow, especially while reading from SD Card
6. My Lumia 720 crashed once and rebooted during WiFi transfer. Otherwise the WiFi transfer works as advertised and is definitely the highlight of the app for me
7. Tested out MKV playback with a low-quality file and everything works well - the playback, scrubbing, swipe to control brightness/volume. But the embedded subtitle did not work, I haven't tried out separate subtitle files - .srt, .sub, etc.
8. This is more of an aesthetic issue than a functional one - the folders icons are ugly. We are used to visually appealing apps on WP, I mean we're not on Android, are we?
Bottom line: The app definitely has potential but is unpolished/beta at best in its current form. $2.99 without trial is also a bummer, so can't say it's money well-spent for now. Hope the promised updates fix all the issues.