One feature I enjoy in Windows 7 is the Windows Explorer's Preview Pane. Will something similar be added to Nautilus for Ubuntu at some point in the future?
Gloobus preview might be the tool you are looking for. I think it is the thing which is included in nautilus elementary, but it can be installed separatly too. For instructions on installation, look here.
It is possible to combine the Gloobus Preview interface with Nautilus i.e. so that you retain any new bug fixes for Nautilus through the repositories but also have the ability to preview files.
In summary, pressing the spacebar on a supported file (e.g. text, pdf, mp3 etc) in Nautilus will present a preview like this for a PDF:
and like this for a MP3:
If you want to try this suggest use the following packages:
Download and install Gloobus Preview from the PPA here
Then download the Nautilus extension script from here
Install a small addition for nautilus
Then extract the Nautilus extension script you have downloaded.
Install the script using
Logout and log back in.
Try nautilus-elementary, now available on Natty:
Nautilus elementary does a preview of images like this:
The Gloobus project intends to have preview for all sorts of files but they are still developing I think.