Remember, people: what is posted on this forum does not - in any way - reflect the gaming experience of the VAST majority.
A few users on this forum own SLI/Crossfire systems because of their need to play games at high res, on big monitors with all the gubbins turned on. Coupled with the marketing hype churned out by Nvidia/ATi, it's easy to believe that the only way of getting decent frame rates is with a system that makes an average electricity meter spin like a top. Which certainly is not true.
I play HL2/X3 at 1280x768 and while I don't have any AA (8xAF depending) enabled, all the textures and detailing are at maximum. And that's on a 9800Pro with an Athlon XP2000 (at 166x10). The game is perfectly smooth and doesn't appear to suffer from any jitter. I'm sure it doesn't look as good as an 'up to date' system, but considering most of the components are around three years old (at least), it pretty good.
Where am I going with this? Well, I would hazard a guess that most users have systems like I do: fast enough for what we use them for. This would put gubbins like SLI, Crossfire, 32" monitors out of the equation anyway. For those seeking higher frame rates, the mid-range single solutions from Nvidia and ATi will do the business without any problems whatsoever. For a small minority of users, that still isn't enough so they buy a secondary card. All this time, the uptake proportion is decreasing.
Think of it this way. Many, many moons ago, Quake 3 came out and everybody had problems running it because it was so crazily detailed and 'realistic': Carmack's new engine was good for a very long time because it hand longevity. Nowadays, a lot of the users on this site are mortified if their dual-core'd SLI'd rig can't push 100fps on the latest game engine. See the difference? SLI/Crossfire are merely there to remind us users who has the fastest technology: those lucky enough to own such rigs can experience the performance of tomorrow today. The rest of us just get on with it.
Hmmm... that's a bit OTT for this forum. Oh, well.
