In a relatively money-no-object situation (we're having a very good year!), what's the ideal Director's monitor for field and studio use, with two video inputs, for the EX1?

My guess would be an Astro oscillo/vectorscope. Over beeing a good monitor, you will have all the needed tools in one.

Then you will have the panasonic BT-LH900 or the Carrion (search forum for informations) which have a 1024x768 resolution in a 8" monitor. The panasonic also have a zoom mode and a small histogram. You can really work with them. I wouldn't go for something smaller than 8". Bigger is heavier, sometime for the same resolution.
The new TV Logic series seems good too but, as far as I know, are 800x480.

They all have HD-SDI, which is the best way to go with the EX1, and some other inputs as VGA, DVI, componant, composite, depending on the model.
I wouldn't go for cheapest brand (Marshal), which does not have HD-SDI inputs.

Hope this helped.