Matt @ MS has a good post on verifying MP workflow on the agent managed computer, but there are a couple of things to be added here that are of value in checking for MP updates being delivered to an agent that do not involve reading XML output.

So Matt hit these three :

#1 Effective Configuration Viewer - Probably the best of the three options listed, availaable HERE.
#2 Health Service Task - To display this from the UI, make sure you target ‘Health Service’ instead of ‘Agent’ if you want to see your management servers. Here’s a detailed how-to from way back is listed  HERE. As mentioned this is a bit ugly.
#3 Powershell Script - This works, but’s it’s ugly 2.0. (Available HERE).

What other methods can tip you off that the change is received? Here are a couple of options.

#4 Operations Manager Event Log -  On the target agent machine, you’ll see event ID: 1201 fromsource HealthService with the MP name and verision in the event description that was just updated. Pretty clear evidence, and no xml required. Incidentally, event ID: 1204 from the same source tells you about MPs that are no longer needed and are unloaded. This is an easy way and pretty safe I think if you don’t have folks making ad hoc changes to your MPs.
#5 MP xml files on the agent - This is not my favorite either, but provides a clue as well. In the agent installation directory under \Health Service State\Management Packs,  you’ll find the MPs running on the agent. You can also check the date/time stamp in the ‘last modified’ column. When you see your target MP with a time stamp from a moment ago, that’s your hint. Since it should be accompanied by a HealthService 1201 event,  I don’t see much point.

I think I like #1 and #4 together. You can use effective configuration viewer and watch for the event and I think that’ll do in most situations. But in the end, this is easier if you have some measure of change management in place to prevent ad hoc changes.