I have my dream camera, 1DMkII, a jack-of-all trades! Not 4MP of the 1Dino, nor 12MP of a 5D. Not 1.6 crop factor, nor full-frame. Excellent AF system, weather-sealing, and excellent burst mode.
I can easily swap this baby for a good condition 1Dino *and* a 5D! (I can eBay it here in Brazil for $3,200)
This is how I would use them:
Walkaround: 5D + 24-105/4L IS
Landscape: 5D + 24-105/4L IS
Travel: 5D + 24-105/4L IS
Low-light: 5D + 85/1.8
Ballet: 5D + 70-200/2.8L IS
Macro: 5D + 50/2.8 EX Macro
Outdoors (wet or rainy): 1D + 24-105/4L IS
Basketball: 1D + 85/1.8 (or 5D and practice timing)
Baseball: 1D + 70-200/2.8L IS
PJ: 1D + 24-105/4L IS
Reasons being:
1) Traveling with a 1DMk2 is very heavy and cumbersome in amusement parks.
2) Landscape would need a wider lens, e.g. 16-35/2.8L, and would add cost.
3) Walkaround would be a lot lighter using a 5D and get wider shots as well.
4) Can't beat a 5D in low-light (compared to the 1DMk2).
5) I can get better shutter speeds for ballet with 5D's better high ISO performance.
6) 1Dino is perfect for baseball because of decent lighting.
7) The only place where a 1DMk2 would be great is basketball... but is seasonal and not what I do mostly. I could use either 1Dino or 5D and then compensate.
8.) PJ work means taking it out to the streets (dangerous here in São Paulo), less worth if stolen 
9) I actually would have a backup!
Best of both worlds and a wise decision?

but for now...
I just wished I hadn't sold my 10D+grip...


