Good questions, Chewie . . . for a wookie, that is.
If you don't ever plan on playing any of the "latest and greatest" games (Doom3, HL2, any of the newer MMORPG's, etc.) while on DC power, then there is nothing wrong with the stock 3790 settings. But, if you do enjoy gaming, then 600mhz cpu speed is simply not enough to keep up with the new stuff out there (see my previous posts about choppy Doom3). Other heavy-hitting, non-game software apps will also be difficult to perform on battery power.
Some would say, "Well, if you are going to game, then plug it in and game-on." While this is true, the fact of the matter is, we purchased a notebook that was billed as very versatile. This versatility has been hampered by the fact that the BIOS options for the 3790's DC power settings are extremely (and needlessly) limited.
I don't NEED to game away from a power outlet; but, I might WANT to someday, and, after plunking down $2700 for this notebook, I damn well should be able to do that. The notebook has the capacity to do this if someone at Sager would revise the current BIOS settings.
If you are just going to be web-browsing and word-processing, then you will be pleased with the laptop as is. Battery life will be grand. But right now, if you want to game unplugged, you have to change the BIOS and screw yourself on battery life (when, if the BIOS was better-designed, you could have the best of both worlds).
As for whether or not you can change the power scheme in the Display settings of Windows, yes you can, to some degree. But the 3790's BIOS limits your options to those we've already mentioned even in this window.
The solution would be so simple. Do what other Centrino chipset notebooks do. Let the cpu adjust its speed to fit computer demands. Then battery life and on-demand performance will both be maxxed-out.
Like I said, this issue isn't really going to affect me too much, but it has affected computiac and it still pisses me off that, after paying over $3K in computer and accessories, my 3790 doesn't run like it should (and could).
EDIT: Still, its a great piece of hardware!