I have used Ensign quite some time and now use it exclusively with the IB feed.
re: BSOD
I have never experienced a BSOD with Ensign and suspect that your problem with that is, as others mentioned, driver related.
HyperThreading at one point did present a problem with the IB feed, but that was during Beta testing and is COMPLETELY resolved in the latest production release (I am on the one dated 12/21/2005, but there is a 3 Jan 06 version, as I just discovered).
re: multiple monitors
Ensign can be used across any number of monitors, so just be sure you understand how to configure the monitors correctly. You won't have to do anything to Ensign, just "drag and stretch" it across the real estate.
And YES, you can put only one chart on each screen is that is what you want.
You can actually do this even with one monitor, by moving charts so they are "under" or "above" the current montior boundaries and thus you have several "virtual" monitors by scrolling up/down or sideways. This is one of Buffy's (Bline room) tricks that she's shared with people only on one monitor.
re: DEMO
You can open as many DEMO charts as you want. The "trick" is to set up a DEMO workspace with your charts pretty much as you use them. Then, once you open the "one" DEMO chart off the DEMO start-up screen, switch into the pre-saved workspace where all your other DEMO charts, with your set-ups/indicators, are all ready to go.
Good luck.
amg