The update with the patch for Spectre and Meltdown is sitting behind a permission wall. I could easily uncheck them and send the rest of the updates on through. The way it's disguised with innocuous wording doesn't fill me with much hope. Yesterday I had created a restore point before connecting to the internet.
Dare I install them?

What are you worried about if you do install them?

Unless you run a server or a cloud service, you won't even notice a change in performance.

It is not true for every system - older PC setups are noticeably affected.

It really boils down to what you're more afraid of: are you more afraid of your rig being hacked and having someone steal your info/passwords/etc or are you more afraid of a performance drop?

Well, stealing data is one thing, but loss of data is another, and I think it's more important for users.

What do you mean "loss of data?"
And where are you getting this "older setups" fare worse info?

Any "innocent" intrusion which starts with stealing passwords can be finished with taking control over whole PC and losing data / files in the end. From Microsoft itself.

Call me a conspiracy nut, but this almost sounds like another Microsoft attempt to force users into "upgrading" (downgrading) to Windows 10.

It's important to remember that these weaknesses have existed for a decade or more. It is not the case that we are suddenly unsafe.

And, reading the article you quoted, they say that only 1 of the 3 variants cause the slowdowns even on older machines. Do you understand what "variants" they are talking about?

Yes, it really feels like it, indeed. You can add another fact to it: last free upgrade option to Windows 10 (for Windows 7 users) ended at the end of 2017.... Can you see that pattern? :D

The truth is that a few my friends with older machines reported some slowdowns... it still needs to be evaluated more precisely.

It is so wrong to think that way. Yes, they existed for many years, but there was no public knowledge about them. Now, these exploits are "documented", publicly revealed, so even script-kiddies will try to use them.

You have them explained in the table on top.

Ah, I see the "variants" listed now. Thanks.

Even though they are publicly known now, I have nowhere seen it stated that any old "script kiddie" can exploit these security weaknesses. You'd have to be targeted - and targeted by someone of high skill.

It is a real security exploit and needs to be patched, and the industry is working on patching it. The first patches are slowing some things down - but again it's mostly the cloud computing industry hurt by the slowdowns - private users are not really affected unless running their own server.

But being alarmist and conspiracy theorizing are not helpful.

One of the reasons for such opinions after reading internet reviews is that probably most "slowdowning" patch requires BIOS update and most BIOSes are still "under construction" - so most users are still before that step.

Im using a Westmere EP and a Haswell computer and haven't seen a slowdown on either one - using the "fixed" OSX version at least. I don't think it will be dramatically different with Windows. if the most recent Win 10 updates include the first patches (at least it installed something when i used Windows today) then i didn't see a major decrease in Windows either.

Don't think the average user will see much of a difference, supposedly its mostly the high I/O server stuff thats more severely affected.

EDIT: That said, never harms to do a quick backup before changing anything about the OS ;)