I actually run three computers and I like the setup a lot. ( 2 PC's and a Mac laptop) I use one main PC as the central device and the other two are usually being virtual synths. On the main computer I am running Studio One and Sonar and various other things like FL Studio. On the Mac I have Pro Tools, Logic and Reason. On the other PC I have an older version of Logic but use it mainly as a VST.
I can get all three working on the same page but one of the advantages of this type of arrangement is that you can also use them all separately which is a bonus and it is in this mode that a single computer won't compete.
My main controllers are feeding all three which means I can record on any of them. I use midi to communicate you don't need Radmin or anything like that. I have midi interfaces connected to all the machines and this allows you to still use one main machine and talk to the other two very easily. The speed of midi is easily fast enough to do this and without any latency.
Audio wise I have got analog and digital signals passing between the main machine and the other two in both directions. The latency depends on the interfaces you are using. With the Mac laptop I have got an Mbox 2 mini and it can be set as low as 32 samples so it is fast. My main machine has an EMU interface and runs the PatchMix software. This handles all the incoming and outgoing audio very well and without issue.
Although I can get all three sequencers to run in sync I tend not to do that and keep the whole musical arrangement on one machine. it is much easier that way. If the others are being VST's all you have to do is keep track of what synths and presets you were using at the time. It is very possible to recall very complex mixes with ease and accuracy.
The Mac laptop is also great for running tutorials and things like Groove 3 videos while you are working on your main computer.