The demo for Nancy Drew: Trail of the Twister has just been released! It's on the main page of the Her Interactive website! Just click on the screen to download the game.
I only played it for a little bit, but it seems good so far. I'm currently working on my super-long, top secret video walkthrough right now, and as soon as I reach the first stopping point (which is about fifteen videos in), I'll immediately switch gears and do a walkthrough for the demo.
Spoiler alert: Mr. Krolmeister himself is in the new Nancy Drew game. You can only get his voice mail message in the demo, but he sounds like a great character.