Ableton Live Intro is the new entry level version of Live which includes ReWire. All existing Live 6 LE and Live 7 LE customers can get a free upgrade to Ableton Live Intro direct from Ableton.
Do I Need Live Intro If I Use A Novation Launchpad or AKAI APC40?
Please note that both versions of Live that ship with the AKAI APC40 and Novation Launchpad do have ReWire enabled. However, these two hardware products will only work as basic MIDI controllers when Ableton Live is a ReWire slave. You get the full two way communication between hardware and software when Live or Live Intro is used as a ReWire Master.
Furthermore, the two main benefits (there are many smaller benefits) of Live Intro over the Launchpad and APC40 Live Editions are track count (unlimited in Live Intro and restricted in LP and APC editions) and the 7GB of content that comes with Live Intro!