For newly trained physicians Kristin and Brian Gillenwater, mornings are a rush. They grab a bite of breakfast. They get Henry, their 1-year-old, ready for day care, then drive off in different directions for a busy day seeing patients.The Gillenwaters don't head to their own practices. An independent practice doesn't hold the same attraction for them as it did for earlier generations of physicians. Independent practice means managing a business and working long, unpredictable hours for what's become an increasingly less certain income.