I had a couple different Crossfire setups, then 8800 GTX single, dual, eventually triple.
Ah, the 8800 GTX. I remember it well. It was a massive game-changer for nVidia. I wasn't playing any big 3D games yet at the time and just had an 8500 GT. I remember that the 8800 came in quite a few flavours with the 8800 GT, 8800 GTS, 8800 GTX and 8800 Alpha Dog. It was so ahead of its time that all nVidia had to do was switch its connectivity to PCIe2 and rename it the 9800 GTX (and then the GTS 250).
This was when I worked at Tiger Direct and I got interested in the latest games (like Crysis). I was initially looking at getting an Intel Core2Quad Q9400 and a BFG GeForce GTX 260 but... when I saw from that side of the counter what Intel and nVidia were doing... I got a really sour taste in my mouth. When I saw that I could get the same performance with a Phenom II X4 940 and a Radeon HD 4870 for about $350 less money, I went with that and have been all-AMD ever since.
Those were replaced with Radeon HD 4850 Crossfire (still have one in a box as a spare) unlocked to HD 4870 shaders.
That's awesome. It's so cool having those old cards around. I love the fact that I still have both of my HD 4870s. I remember when I got my first one, to make my buddy at work laugh, I hugged the box close and stroked it while whispering "MY PRECIOUS!!!".
My last multi-GPU setup was dual GeForce 980Ti.
Which coincides perfectly with my last multi-GPU setup of twin R9 Furies.
By that point it was already pretty difficult getting things to make use of both GPUs.
Yes it was. It sounds like you were as frustrated with it as I was.
I also miss multi-GPU and kind of wish they'd bring it back, but given how much power modern GPUs draw I don't think that's a great idea. We'd be back to needing 1600w PSUs overnight.
What I liked most about Crossfire and SLI was the fact that you could upgrade your GPU simply by buying another of the same (or in the case of Crossfire, similar) type. You were still able to leverage the power of the card that you already had. That made upgrading less expensive (because by the time you needed to upgrade, it was a sure bet that your card had become really cheap to buy) and it also meant less e-waste because it made cards longer-lasting and thus, less disposable.
As for the 1600W PSUs... I think that's an inevitability regardless of what we do based on the way things seem to be going.