They have been pushed on the deaf community as a cure, but for those who have never been able to hear they are not ideal and a fair number want them removed.

If you are implanted after the speech window is closed (some providers quote age 7-8 years of age), then the utility of implants dramatically decreases. For implanting kids, the younger the better, and the results can be outstanding with supportive parents and good providers. The downside to getting them for kids is really... nothing (aside from enduring the wrath of the deaf community). If my child decides to take them off as an adult, I would fully support him. I suspect, however, that he will not want this as he is now fully integrated into a hearing world (which includes excelling on a musical instrument... something I did not think would be possible). He hears and recognizes 95% percent of speech (on par with most hearing children his age). Pretty incredible...

You are correct that post lingually deaf adults (those who lose hearing later in life after a life of hearing) are usually great candidates for implants.