...I would consider it a more of a pain than intrusive. ...
I would say that all DRMs are more or less pain and intrusive. How could any DRM work without being intrusive? There must be a checkpoint at some point.
There are two different potential annoyances for me with DRM:
1. How does it affect and restrict installing and playing the game now?
2. Does it cause any potential dangers for the future, if I want to (re)play the game in the (maybe even distant) future? This is also important considering I quite often buy games into backlog, and play them much much later from the purchase day. I have loads of games I've bought years ago, but not yet even installed once.
It seems some people feel that as long as #1 is fine (e.g. it doesn't require being connected all the time), the DRM can't be considered intrusive. But soime of us care also about #2, because we don't want to consider the purchases mere "long-time rentals" that might be revoked without our control and consent (and the arguments that "you might still not be able to play the game in your future PCs, DRM or not!" are completely irrelevant to this)..
Someone who installs games only once soon after purchase, and throws the game away after finishing it or getting bored, doesn't necessarily consider it intrusive if there was e.g. 3-time installation limit for the game. He used only one of the installations anyway, so why should he care? It was completely transparent to him. But for someone else it may matter.
There was the example of limited activations, where the activations would be automatically increased or resetted every now and then. But that still depends on someone to do that resetting in the future, someone who might not be there in 5 years if I want to re-install the game. In fact, if the authentication servers controlling the installation limits were offline, you couldn't install the game even if you still had unused installations in your pocket.
So while I would find such scheme unintrusive _now_, it might have become intrusive in 5 years.
To give some kind of analogy: Rise of Legends (a 2006 game) has a system where you download updates for the game in-game from their update servers, and no offline updates were ever offered.
Back when the game was new, anyone could argue that it is not intrusive, and no one has anything to complain about it. The update system worked great back then (I presume).
Until one day, they put the update servers offline. So when I recently installed the game and tried to update it, it couldn't update itself anymore due to the original update servers being offline. Something that was unintrusive before, has now become intrusive.
A bit similar case with various Starforce copy protections and such. For 99% of the people, they worked fine and were pretty much transparent back when the game was new. But when you try to run the game later on some newer Windows version, it may be simply that damn same copy protection that suddenly makes you unable to play the game. So it was unintrusive back then, but intrusive now.
Then again, one could argue that you can still play the on the original system it was intended for (e.g. some a bit older 32bit Windows XP PC, not a 64bit Win7/8). But it has still become an _extra_ impediment later to play the game, something that it wasn't before.
Thus why I'm asking for 3dfx exclusives. Not sure if there were any, since I can't find any at this point, but if the game required a voodoo card to run, and wouldn't run without one, isn't it equivalent to not running if the dongle isn't found on the PC?
If you had medium graphics without the voodoo, but great graphics with the voodoo, that isn't a requirement to run.
Besides the special 3Dfx versions of games like Mechwarrior 2 and Fatal Racing that were delivered only with new 3Dfx cards, I don't think there were. The retail versions of said games still worked also without 3Dfx cards.
Anyway, even if the was, I think the point is the motivation. If some game needs minimum 4GB of RAM, it is not DRM/antipiracy/copy protection unless the motivation for the restriction was not to allow people with less RAM to play the game, and not to make the game better with more RAM.
EDIT: Come to think of it, the motivation with 3Dfx specific Mechwarrior 2 and Fatal Racing was to limit the usage to systems with 3Dfx cards.