My comments on iPrint/NDPS. . .

1) Authentication and encryption should be separate functions. Currently
you cannot have one without the other.
2) Single sign-on. If Client32 is installed, authentication should pass
3) Users should only be able to see printers they have access to in
http://server/ipp and on maps created by maptool.htm (maptool should support
NDPS printers). Users should also be able to use same tools to select which
printer they want to default to.
4) There needs to be a simpler way and better tools to provide user and
workstation based printing.
5) RPM Configuration will only set default printer if printer does not
already exist. Would be nice if this tool can accept workstations and
install iPrint printers.
6) Other than clustering, there is no easy way to provide fault tolerance
for broker.nlm.
7) If you can load multiple NDPS Mangers on a server under different address
spaces, then you can restart a NDPS Manager without affecting all printers.
8) Better printer driver handling required. Should be able to allow
multiple printer drivers per printer (i.e. choice of PS or PCL driver or
both). Auto upgrade of drivers versions. Set specific printer settings.

If I've mistaken on any point, I would appreciate it if someone can clarify.
These are the things I noticed when moving over from queue based printing.
I realize there are workarounds and 3rd party solutions for some of these
but what could be better than built-in native support of these functions?

Because of items 1 thru 5 above, I ended up using NDPS printing instead of
iPrint/IPP printing to workaround and provide for what I need. I have this
long login script for user based printing and I'm using app objects for
workstation based printing and pushing down drivers when there is a local
printer attached to a workstation. Also using LPR from Macs and Linux.