Optimus is a Radio Shack brand name - so I have to assume your keyboard is a Radio Shack device, which would make it a consumer level unit in the same basic market as lower line Casio or Yamaha consumer boards.
I don't know about your keyboard, but in general consumer level keyboards are designed for students or for home hobby players (vs. semi pro or pro players).
This means the sounds tend to be weaker and the editing capabilities are not as deep. Your board may be fine for home recording, but it lilkely could not hold up to road abuse.
It is unlikely there will be any written reviews (such as in the gear magazines) since it is a consumer board
IS it any good? That depaends - Do you like the sounds? Do you enjoy playing it? Can you find a use for it? If you answer yes, then it's good (at least for you).
Perhaps a Radio Shack good give you more info.
