The Digi003 will require Digidesign's Core Audio driver. It is usually an optional install when you run the PTLE installer. Otherwise, it's on the original disk or you can download it from the Digi site. It will probably work just fine. I've been using LP7.2.3 with my 002R and an RME interface as my main i/o. I actually only use the 002 interface as an expensive dongle or as a quick and dirty interface for demos. The RME is used for serious work, gets all the i/o and talks to the 002r via ADAT lightpipe. LP7 recognizes all 17 i/o, so I'm hoping LP8 will, too. My LP8 is arriving tomorrow, so I'll know more then. I have heard that the 003 is a much superior product to the 002 - in just about all specs.
You only use DAE if you have TDM hardware. However, I understand that LP8 now works with TDM hardware on Intel Macs - LP7 did not. It only worked on the Motorola/IBM chips (g4/g5).
OS10.5.8; Dual Nehalem 2.26Ghz/6GB; Logic Pro 9.1; PTLE/002R/RME; Waves Platinum; lots of other plugins