All user reviews for the Roland SD-50

Interface audio quality
Zero latency
MIDI sound varied
Sounds interesting solos evolutionary
99% used as external MIDI expander
mic preamp for a mix of basic troubleshoots well (cool little reverb)
Used on PC and Mac

UTILIZATION

Impeccable stability on Mac and PC
Using 99% as the expander software Expresseur
Zero latency

SOUNDS

Trouble-free installation
Easy config
Fairly complete manual on the Internet

OVERALL OPINION

Used last year
More comprehensive than other MIDI expanders (product which is rare)
By definition, can have a very good sound with any little tiny computer
Much easier to use than VST that require powerful computers with super-audio card for zero latency and good sound.
A little expensive compared to a digital piano. But hey, there is little competition in the niche. The product is complete.
I would buy one more good for the quadraphonic ...