What is the role of the Shaliach Tzibbur (Shatz)? Is it to lead prayers or to pray on behalf of the congregations? Does this role depend on the nature of the congregation? For eg, should a Shatz read the repetition (and perhaps other parts of the service) more slowly/clearly if many members of the congregation do not read Hebrew verses in a relatively sophisticated and literate (halachically) congregation? Finally, can you explain the term "Tirchat Hatzibbur"? I usually hear it used as an excuse for a Shatz davenning at the speed of light!
The Shatz is literally a Shaliach Tzibbur - the messenger of a congregation at a public prayer, although the repetition was originally established for those who aren't well versed, the Rambam wrote that even if everyone is familiar with the prayers the regulation stays, specially since it is a congregational prayer, and the peak of the prayer is saying Kdusha with a Tzibbur. Hence, it is clear that the Shatz should say the repetition with Kavana and clarity, with the Tzibbur saying Amen with Kavana after each Bracha. The concept of "Tirchat Hatzibbur" has to deal only with things that either have nothing to do with Chazals regulations, or things which Chazal told us to give up on to begin with - if you wish to pursue this subject further - you can see Masechet Yoma, at the beginning of the first chapter. Rabbi Chaim Katz