Well, the first user review on Amazon is up, and it's one star. The purchaser complains that the sound quality seems "less sharp" which could mean anything, but more significantly he comments that the remote app is nothing like advertised. Here he may have a point - on the app download page for Android, the description says that it's a beta version with missing features, which is a bit poor from a company like Tascam. I've installed it in anticipation, and when I run it, all I get is a message in Japanese (or something) and a single button to click, which then exits the app.
Now that could be simply because the app can tell that I'm not connected to a Tascam wifi network, but an error message in English would have been more helpful.
Anyway, now the app is installed it will update itself as Tascam gets its act together - hopefully - with any missing features added.
UPdate - having looked at the comments on the iOS app store, it's necessary to update the device and its wifi firmware before using the app. This could be why users are having problems.