One feature i miss a lot in gnome2 is to right-click a file on the desktop
or in the file manager, select open-with and get a new window with options
(where aplicable) and the option to select another program (run dialog?)
and 'always use this' checkbox..

Currently open with has a sub-menu, which then has a few options if it
knows of programs that can handle the file, "Other Application" and "Other
Viewer". Now i do not think a beginning user knows what the diff is. Worse,
they seem to open the same screen for for quite a few files.. puzzeling and
confusing. Going there, i am greeted by a complex and tech-looking dialog,
 a "modify" button that gives me a slew of weird options; A "go there"
button that brings me to a more complicated dialog that make no sense to
me, and no way to go back to where i was before.. Also the name "Choose" is
confusing.. i would expect a selection dialog there (choose a program
right?) but instead it seems to run the app.. All in all a lot of places to
get lost and confused; Not to mention generaly intimitated by the desktop.

It would be simpler if we had one default inline-viewer for nautilus (and
hide that prefs in a control center dialog) and open-with would directly
open the "Open with other application" dialog.

That dialog shows a list of programs that are appropiate (preferably icon +
app name, maybe lift that code from the run dialog?), a "other program"
button (opens a file selector) and a "Always use this program for files of
this type" option/checkbox.

I think in this way ppl would be more confident in using this feature, and
be less confused/intimidated. Using wording such as "Always use for files
of this type" sounds a lot less intimidating then things like "default for
tar archive (gzip compressed)".. i would hide most mime-type names from the
users, especialy 

The ability to choose "Don't show this program as an option for this type",
"Show in menu" and "make default for this file / all files" in the
"open-with" menu is a bit more power then users need (and over complex). 

I could understand that having all these extra options for customising how
your OS behaves do have value, but making them accesable thru nautilus
menu's seems a bit overkill, and would make it to hard to use for end-users.