There's a fantastic video about the differences between Astropad and Duet on youtube. Basically, it comes down to if you want a display, Duet is perfect for being a display. If you want responsiveness, Astropad has a variable bitrate to compensate for the fast touch of a brush / pencil.
Duet is designed to be just a screen, heck, it's designed to be the best option for using your ipad as a monitor.
It's just not a graphics tablet like Astropad is.
I don't think that is true for the new version. Duet is definitely faster if you compare equally (mirroring) while duet can also do a second display
Yeah that video was before the Duet Pro public launch, but it was still outdated and factually incorrect even at the time.
I tried duet the other day to play with photoshop, whilst it was cool, it was slow.
I'm going to try astropad next as a text to see if that can turn the iPad into a hybrid wacom style device.
Can you e-mail us? It should definitely not be slow.