I always demand (excuse me, "suggest") to editors that they give me a final conform XML with no more than 2 video tracks and no more than 2 audio tracks. It doesn't always happen. One recent project had 9 video tracks, and my head exploded. I was able to manually flatten it to 2 and it worked fine, but it was an annoyance.
Joe's comparison to Tetris is very apt. The only time I can buy multiple tracks is if there's three or four simultaneous dissolves, composites, or split-screens or something. And even then, I think I'd rather have a flattened file unless it's something I need to color-correct prior to the VFX.
For regular A/B dissolves, I'm totally cool with 2 tracks. 9+ tracks for color?... I can't go for that, noooo.... no can do.
