I spent a little time looking at Ruby in the past. It seems like a nicely designed, clean language. However, it seems to me that it lost to Python in many domains. In addition, I've heard stories about Ruby having performance problems. For example, I heard Twitter rewrote their backend in Java/Scala because Ruby didn't perform well enough.
Recently I was at a Cloud Computing symposium thing attended by academics and industrial developers. No-one in the room was using Ruby for development anymore. Has it died? Is there any point learning it?