The knives are out for Oprah and the best her detractors seem to have is a few questionable health products. Any politician with any level of experience has taken money that most people would consider dirty and done favors in return, made terrible votes that have hurt a lot of people, and compromised lots of principles.
Again, she is strategic and clearly a good learner. By the way, I suspect she is among the very cleanest self-made wealthy people: no insider trading, no regulatory arbitrage, no polluting industries, no sweetheart government contracts.
Ability to think and learn is more important than experience. Consider Al Franken, who entered the Senate from a career as an entertainer and turned out to be a more scholarly, detail-oriented and effective a legislator than nearly any of his counterparts.
This is not specific to Oprah. I would be happy to elect a concert violinist who developed a skill at an astonishingly high level and then figured out to work within the system to make a career by standing out from all the other astonishingly skilled players. I would not be happy to elect another privileged and entitled idiot with good hair who rose through demographics and luck, regardless of how many legislative offices he has previously occupied.