Caving to market pressure, MRO Software Inc. quietly withdrew its offer to buy Datastream Systems Inc. Facing Datastream's rejection and analyst scrutiny that the deal wouldn't provide any long-term benefit for Datastream shareholders or customers, MRO, which had vowed to move forward, has had a sudden change of heart. "We evaluated the hostile route and decided it was not going to be the best use of our resources," says Vaughn Harring, a company spokesman.