Just how important are these MS updates?

Microsoft has left some .NET Framework updates behind as optional (and that shows in your list). Then applications that depend upon .NET Framework sometimes do not work properly.

I do all the updates (Critical and Recommended) and do the same for my clients. Experience has shown that this is a good practice.

.... Thinkpads_User

Be aware that some applications are .Net specific and require a specific version. Installing later version can break applications depending on what they require and or compatible with.

If you have done patch management in a windows environment .NET updates should not be part of the roll out for this reason.

Will.

I avoid applying the hardware-specific driver updates that microsoft recommends in the Optional section. They break things way more often than helping.  $0.02

I agree about hardware specific updates. I get those from the PC manufacturer instead. I do see however that vendors are starting to work with Microsoft on this issue.

... Thinkpads_User

Yeah...  there weren't any in the OP's screen shot, but just thought I'd mention them.
Anything more and I'd be hijacking the thread, so I'll just back out quietly now.  :)

Thanks everyone for all the excellent advice!

@ArtG2521 - Thanks and I was happy to help you with this.

... Thinkpads_User

ArtG2521--You are welcome.