As for rebates: None are available for this drive, so that's not an issue.
As for warranty: It's not a hard and fast fact that OEM drives have shorter warranties than retail versions, and the point is we really don't know here. Plextor has a reputation for taking care of its customers. I have a hard time believing that if this drive dies on you, they won't help you out.
As for the included media: The retail box includes one CDR and one CDRW (not even plextor's house brand, ironically. Can't remember, but I think they're verbatim). As for the software: It includes EZ CD Creator and DirectCD (the latter for CDRW writing), as well as something called Plextor Manager which includes a media player, audio ripper and a couple other utilities.
Plextor manager can be downloaded from plextor's web site. As for EZ CD Creator: I like it, but lots of people hate it anyway. There are free programs you can download to tide you over, or you can go buy something like Nero.
The drive doesn't require any drivers for use, so the only "software" they're giving you is software for burning CD's.
Also: Since NewEgg clearly states "with software," I'd bet they're throwing something in. They could have a bunch of oem versions of EZ Cd Creator (since just about every CDR drive comes with it these days), and they could be including those.