The -current snapshot kernel-image disk boots on my machine, but
   doesn't recognize the 4Xe either.

The words `doesn't recognize' are *extremely* vague.  What, precisely,
does the kernel display when it boots?

   This note is a revision of a message that was posted yesterday on
   comp.unix.bsd.netbsd.misc. Since then I've had some e-mail from
   someone (Robert Yoder) who thinks that the Adaptec 1740 class host
   adapters have trouble with all NEC SCSI cdrom drives under NetBSD. Is
   there a consensus out there around this point?

That's absolutely false.  I have a NEC drive here that I've been using
alternately on a 1742 and a 1522.