Should be getting mine within the next few days and I think it is worth the wait. My test piece was really fast (faster than the DW1620 using the same media) and the burns gave beautiful scans as well, can't show them screenies though (NDA still!).
Are there any advantages of the NEC 3540 over the DW1640, besides DVD-R DL? Somehow, I feel that DVD-R DL is an obligatory wannabe product from the DVD Forum trying to do catchup to +R DL.