I can subscribe to most of what ajnaro says in his post. The hotel has a nice pool area, though, and SPG platinums get access to the club lounge on the 4th floor where you have nive breakfast and food offerings during the day.
I stay there every time I go to Rio for business and whereas one should always take care (ie use common security sense) when walking in public areas in Brazil the "standard" crime advisories are generally overstating the risk. Most Americans forget to look in their own backyard when they describe public safety abroad and Brazilians are always talking their own country down when discussing tourism with foreigners...it is something of a national passtime! So my recommendation is: Go to Rio, Stay at the Sheraton, use common sense when doing your sightseeing and enjoy. Yesterday the US$ was worth 3 Reais so the value for money is excellent.