OK, I'm not sure which part of my short reply was condescending, but I didn't intend to be. Things were pretty much OK in Aperture up until about 35,000 images, at which point things started to get very buggy. I think it's a volume issue, and the only way to test it would be to have a great volume of Raw files loaded into a program. Hence my query to see if anyone else has this situation and is getting better results than I am.
Yes, I'm using Aperture 2, and I said in my original post that I prefer it over Lightroom because I have used Lightroom (otherwise, how would I know that I prefer it?). I actually started out with Lightroom and then migrated to Aperture because of the dual screen support. Now I'm wondering if perhaps that was a bad decision.
Thank you Grimace for a very helpful reply. If you're up over the amount I'm at with no problems, then my system must be to blame. I'm frequently getting a black frame instead of a second image on my second display, or sometimes a checkerboard of black plus the image (divided into four quadrants). Very often when I go to edit an image, I'll make some minor adjustment and the whole image turns almost white with bits of cyan or yellow in the image still showing (as if the image were grossly overexposed or something). Then there is the random red "file type not supported" screen. I can't work in Aperture for more than a few hours without one of these things happening, and lately, they've been happening immediately. It's really frustrating and is a major time sink.
My system is hardly what I would call pro. I change locations (between Europe and the US) about four times per year, so I need to stay mobile. My solution has been to travel with a laptop and a couple of hard drives, with everything else (monitors, keyboards, mice, etc.) duplicated in both locations. It's a difficult situation. I can't possibly schlepp a MacPro back-and-forth with me, alas.
