For those not convinced that poly strings cause TE... the problem occurs when the strings go dead, which is usually after about 2 weeks. When the strings are fresh they feel great and are probably still safe (at low tensions), but since they don't move around or show wear, people usually don't change them for months.
The reason the pros can use them without problems is because their racquets are strung fresh after every match and every practice. They never play with dead strings!
So unless you plan to string your racquets OFTEN, forget poly or you're asking for trouble.