For many visitors the world’s highest commercially navigable lake has lost a lot of it’s charm. On all itineraries will be a visit to the Uros islands. These are floating reed islands of which many of them have been built especially for tourists making them more of museum pieces than real life islands. On Amantani island you can sleep in the houses of the locals. At night the mamma’s dress you up in local clothing and take you out dancing. Many people might think all of this is really phony (especially when they start singing "my bonnie lies over the ocean") but it does give a decent insight in the daily life of the local Aymara people and it provides the local people with an income.
Another Peruvian Titicaca island to visit is Taquile, again very touristy. A visit to Titicaca can be very fun and very rewarding but a lot depends on knowing what to expect.