how brain dead is AIX?

[jsm at ss01.pppl.gov]

I have a copy of 'IBM RISC System/6000 Software Offerings Overview' brochure.
I am a little worried about two of the statements made: 

A) When there are conflicts, they are resolved with priority 1) POSIX
	2) SVID 3) 4.3 BSD 4) AIX/RT. (p. 3). 

   I gather that AIX is System V kernel with the Berkeley stuff emulated.
   So, do you get:
     1) the System V file system or the 'Berkeley Fast File System'
     2) streams or sockets
     3) job control (control-Z)
     4) AT&T or Berkeley terminal device driver.

B) 'Most 4.3 BSD commands, system calls, and library routines are supported.'
 	(p.3) and features include a '4.3 BSD compatibility library'.  (p.5)

  Ok, what is missing? 

One more question: we already have several BSDish systems (Dec- and Sparc-
  stations).  Things are currently seamless: all programs we have needed so far
  will compile on both and run fine on both. Would the same be true of an AIX
  system? Will we have to hire someone full time to support the AIX? How many
  lines like '#ifdef AIX' are there in the source code for gnu-emacs? X11R4?

	Thanks,

		Scott