I've been struggling a bit with the tiny preview window wishing it was bigger. Lucky for me I run a triple monitor setup so when I read about additional windows I got pretty excited, until I found they don't work for people using NVidia Surround like I usually do. I switched to 3 x multi setup instead, pressed the button, and immediately slapped a 3D view on a second monitor.
That lasted for about 1 minute, until a build sent the result straight over my device view. No biggie, I moved the device view to the other monitor and giggled with glee. Right until I went to bypass a device by slapping 'B'. It didn't work, none of the shortcuts work. I move it back to the main monitor and it's all fine.
Just a heads up, since this would be nice to have working.
Apart from that the feature is just great. The main view updates as I move sliders, and it gives a pretty good view of what my changes will do so I am very happy. This will really be invaluable for trying to get snow looking right on my sizeable (32km x 32km) terrain. I'll be cutting that down a bit with an extent to speed things up.
Speaking of extents. I tried making one and changing the top right co-ords also changes the size of the extent. Is this expected behaviour?