Linux (Ubuntu) make an ISO image of a CD or DVD in one step

Two frequent recommendations made online for creating ISO images are to use dd or cat e.g. For example:

dd if=/dev/cdrom of=cdimage.iso
cat /dev/cdrom > cdimage.iso

Neither are appropriate to create an image of CD or DVD.
  1. They provide no error checking and require a hash checksum such as MD5 or SHA1 to verify the image created is true to the original media; and
  2. Neither dd or cat lock the underlying files so there's a risk they could change whilst the image is being created.

Use readom...

Ubuntu: 12.04 Precise Pangolin Where are print screen / screenshots saved? missing dialog prompt?

Previously under Ubuntu 11.10 & Gnome when I pressed print screen 'PrtSc' on my keyboard to take a screenshot, it worked It presented a prompt and asked where to save the screenshot. 

Now I'm using Ubuntu 12.04 still with Gnome, hitting PrtSc makes the  screen flash as if a screenshot has been taken but I get no save prompt or dialog. The screenshots don't appear to save to my desktop (where they previously had) whilst using Unity I do get a print screen prompt. Odd.

Q. Where has the print screen prompt gone and more importantly where are my screenshots?...