A priceless quote: "Never in the history of man has a software developer said "I'm stuck doing Ruby for my day job but I'm really hoping to find a job in .NET or Java.""

Use the right tool for what you're doing. Ruby (or PHP) is great for rapid prototyping. But you won't want to use it if you need distributed processing. Also I feel more productive when I learning when I'm doing. Sure gems gets you more features, but how much have you really learned vs building it yourself?