Great conversation thread! I am not a telco business guy, but am the telco guy for the small manufacturing company for which I work (Northern Tel SL-1). I also support the computer network, and mostly provide manufacturing support and improvement.
Ever since I started doing anything telco (about 25 years ago, with an SL-1, a TIE key system, an Electra system) I was amazed at how primitive the programming interface was, but mostly how convoluted and spagetti like changes were (like:to enable a feature you have to make 4 changes in different places). Maybe the newer SL-1 PC interface fixes all this (I got old software on mine), but the NEC DSX-40 system I just bought (and had high hopes for it being much easier to program and talk to) has exactly the same program interface as the TIE and Electra of 20 years ago. (note: it does have a nice PC/ethernet interface so I can talk to it through a menu setup instead of a keypad!....but it is the exact same 1212-01 type programs steps menuized, not made simpler or more logical.
As far as I can tell,, all the phone system code was written way back when and it continues to be used in the same form.
Now as to IP phones; I haven't set up any, but they can emulate existing phone setup code, or make up their own setup system which I am betting will be clean and easy to program (for the good ones). Since the old style phone system mfgs have not made things easier, the new kids will ultimately do it.
gr