In large skillet, combine potatoes with enough salted water to cover. Heat to boiling; simmer until tender. about 12 minutes. Drain; place in large bowl.
Halve sausage lengthwise; cut crosswise into 1/2 inch diagonal slices. In skillet used to cook potatoes, saute'' sausage over medium-heat until browned, about 10 minutes. With slotted spoon, transfer to bowl with potatoes; add tomatoes.
In small bowl, combine vinegar, pesto, and 1/2 t freshly ground pepper; mix. Add to potato mixture; toss. Serve warm or at room temperature.