I'm sorry, but this... bogglesome... lack of support for the #1 use case of patching is exactly why we stopped using ZPM and switched straight to WSUS. And since we went to WSUS, we haven't had any problems.
Seriously, we tried to make ZPM do the simplest of our requirements, but it was a farce. Pushing out the monthly Microsoft service packs for Windows/Office/IE to all our desktop clients is exactly what we need, and exactly what ZPM refuses to do.
I really, really tried to understand why ZPM's approach was "you only use Mandatory Baselines to update major service packs... which you will generally be updating on your regular image build and pushing out by Zen Imaging anyway, thus making ZPM irrelevant... for all the urgent stuff, you must do it manually". But I couldn't get my head around that kind of logic. Creating all those manual deployment jobs for every iteration of monthly MS updates turned into a full-time job, *plus*, it didn't provide any security whenever an unpatched desktop turned up on our campus. Which happens all the time, since we only update our images on a quarterly-to-yearly cycle, but our helpdesk's first response to software trouble is to restore any broken desktop to the current image, which of course will be several month's worth of patches behind.
"Often I see customers deploying to test machines, then to the IT department and then phasing the deployment to the rest of the enterprise. What’s your approach to testing and deploying patches?"
Yep, that's exactly what we do, which is why ZPM's lack of support for this use case boggles me. Day after Patch Tuesday, we have the latest monthly crop of MS fixes auto-installing on a tiny group of IT staff machines (one room full). A couple of days later, we push them to all our IT machines. A week later, they go to our beta test group (a couple of classroom suites and representative staff machines). A week later, it goes to a single building, finally to the entire campus.
With WSUS, this is pretty easy: each week I just go through and check the logs for failed installs, and if all is well I go through each outstanding patch and tick the boxes to install to the next group of machines. An AutoIt3 script (Zen force run at daily startup) on each machine detects what group it's in based on room, building, machine time, and sets the WSUS group appropriately.
And WSUS is *perfectly* capable, unlike ZPM, of scheduling patches to apply daily, at the hour of your choice, so we make it 6am. And it Just Works.
Please, fix ZPM so it makes Mandatory Baselines as pain-free to use as WSUS!