I bought this as a way to occasionally play a few short sax licks with a ukulele band. For that, it is perfectly reasonable. Begin in C is a huge benefit (no transposing).
If you're looking into buying a jSax, you're not exactly looking for that ultimate sax sound, so I doubt you'll be disappointed with it. It sounds surprisingly good, way better than a "plastic toy" sound, but it's no brass instrument.
As a complete beginner (I had never played the sax before), it was surprisingly easy to get a bit of sound out of it. Practice makes perfect though, you'll sound like a cat in heat for the first few times.
Overall, I really like it. It's an actual musical instrument, but "not very serious" musicians.