Sometimes a company has a mixture of proven performance and upcoming catalysts that make the idea of buying it hand-over-fist practically irresistible. And that's exactly what Vertex Pharmaceuticals (VRTX 0.59%) is modeling right now. Thanks to its long-standing dominance in a key niche market, its newfound pursuit of powerful gene therapies, and its cash output, there's good reason to be excited about the stock. So here are three arguments for why it's worth buying now. 1. Its base of recurring revenue is ...