question about P1 expression library

[User]

Hello netters,
  Since I may set up a screening of expression library in the near future,
I am interested in the advantages and disadvantages of P1 expression lib
comparing with usual libraries.
  As I can remember from college course years ago, P1 is a filamentous
phage with a lysogenic life cycle.  Or my memory betrays me?  Further
enlightment will be greatly appreciated.
                                                                      Jie Li
                                                                     U of PENN