Manso is an attractive place in the morning, as it gets sun about an hour earlier than your campsite in Nido de Condores, which is more in the shade of Cerro Aconcagua.
The elevation of the welcome sign at Nido de Condores is about 18300 feet, which is higher than Cerro Manso, so there is a net descent to the summit of Manso on the route I took. But GPS gives an elevation for Cerro Manso of about 18138 feet (+/-30? feet), so it's not as bad as the official elevation claim of 17828. Manso is definitely an eighteener; the GPS may not be exact, but it's definitely not more than 138 feet off.