I've been trying to turn over Patch Management to a co-worker for a couple of months now, and since training her, PM hasn't been working correctly.

We have systems at various states of patching, and we push patches in different combinations. Sometimes by patch, sometimes all patches for a particular machine, sometimes by a dynamic group. For example we can push 20 patches to a single or multiple machines, and after first making sure that any 1.1, 1.2 dependent patches are removed, the machine will still only apply a handful of patches at a time. The most common error is an 'Unknown' in launching Remediate.exe on the patch being applied otherwise the most common errors are similar to the following:
BUNDLE.ChildActionError{af47eb020a61353eaee6ec5edd 232c48;MS10-036 Security Update for the 2007 Microsoft Of--612618556}

When pushing these bundles to multiple machines, it is possible for one bundle to deploy successfullly on one machine and fail on the next, consistently, which is the frustrating part.

I like the promise of patch management, but with the amount of time and effort that I've put into it, I'm nearly ready to go back to just leaving things up to Windows Updates to make my life easier.