I was at the hotel all of last week and it was a great experience. The Westin is better located for business and touring as it's only 5 minutes from Miraflores where as the Sheraton is closer to downtown Lima, but there isn't much there and the plaza space out front is under construction.
My wife and I have been to properties all around the world and this Westin is definitely a great property. It has the Westin design and service, but a cool W like feel and experience. Trust me when I say that you will NOT find a better pool or spa at any other Westin in the world. It's a sight to be seen. We will be getting some pictures up to Tripadvisor once we get home.
Here is a note I sent to the hotel management regarding our stay.
"... thank you for the follow up email. As I said to my wife during our stay, the Westin Lima hotel is truly amazing. All of the service staff were helpful and pleasant, from the house keeping staff to the restaurant waiters. Since it was a new hotel, I was expecting a level of service reflecting new employees who were still learning their jobs. But that is not what we experienced at all. The training was exemplary and everyone knew their jobs. Other than a problem with printing out my bill on our departure, the experience was perfect. Even the ease of hiring a car to drive to my customer each day or to venture out to another great Lima restaurant, the staff was great. Even my colleagues staying at other hotels were jealous..
I can't wait to return and experience the hotel when the spa is completely open. Until then, please accept my appreciation and best of luck with the new hotel."