I run two PCs with my main on one and the 4 slaves on the other (WoW)
I mainly do it because my processing power is limited, so i have to spread on 2 machines.

What i like about it.
- If for whatever reason i have a lockup due to too many toons or whatever, i can still use my main.
- i can run my main in full settings, with no detriment to the slaves

What i don't like about it
- swapping keyboards whenever i need to do something that can't be boxed well (picking a herb or whatever)
- loading, updating, setting mods or whatever on 2 machines


If i had t a bit of cash i'd get a beefier machine and just play all on 1 with 2 screens (main Fulls screen and 4 shared on the other)