I bought this to use with a Fishman Triple Play Wireless guitar midi system - and it works perfectly - just plug the FTP's USB receiver into the host socket on this, set the pickup to "hardware" mode and play. There's no noticeable latency and every note played as expected. A little tweaking may be useful in the FTP software to ensure that pitchbends and touch are handled correctly according to the midi "instrument" but otherwise, it's plug and play.
As for the PianoBox itself - it feels solid enough, metal frame and plastic front panel. The packaging is simple enough - the unit and a USB A>B cable. There's also a leaflet offering some free software downloads including Samplitude and a couple of VSTs.
The unit itself sounds like an older GM keyboard, which is what I expected. The sounds are obviously not going to compete with today's software-based sounds but that's not what it's for - it's a quick and simple tool for when you want the sounds without using a computer or tablet. The overall sound output is a bit woolly - whatever amp or preamp is onboard could really have done with EQ as there's absolutely no sparkle or top-end on any of the tones and adding more than a touch of reverb to any bass sounds, especially the kick-drum, sees it distorted quite badly at any volume.
And speaking of volume - the volume control on the front of the unit ONLY controls the headphone output. You can adjust the volume on a channel-by-channel basis but that's more about mixing and there's no master-volume (unless there's "undocumented features" on this). Also note that using headphones does not mute the main outputs.
The display is lacking in any useful (essential?) information - it only shows patch numbers rather than simply naming the virtual instrument - an unacceptable omission on a device that only outputs the standard GM sounds. Same with the drum patterns - all you get is a number. The display also fails to show what PC is currently incoming on any channel - another inexplicable omission.
For all the flaws, it's a rarity in 2024 - a simple GM sound module. It's a little pricey for what it is but that's supply and demand for you. I can't compare it to the smaller alternatives directly but I've heard them via youtube videos and against those, this certainly sounds less like a toy. The drum patterns are not bad and the overall output is no better or worse than a home keyboard at the same sort of price. Where this wins is that USB host plus the USB midi AND din midi connections - plus the additional controls with their own buttons. And for me, mixing these sounds with guitar output using the Fishman TP thanks to the USB host and no computer in sight - that's (almost) priceless.