Having the ability to customize emails sent out to 'nosy' 
people would make Roundup much more flexible.  At the 
very least being able to edit the default syntax for the 
'comment was added by...' and 'new submission by...' emails 
would be helpful.

It would also be helpful with a template that can be used to extract information into the email that is not available in the classic tracker.
For example such things as the timelog entries, which can be added as described here:
http://roundup.sourceforge.net/doc-1.0/customizing.html#adding-a-time-log-to-your-issues

In the current email body the timelog entries made are showed as
times: +3
where +3 seems to be the current *count* of added timelog values for the issue rather than the actual value added by the user when he created the current message...

With a template similar to the html templates also for the email message two things could be accomplished:
1) Customized data displayed properly
2) HTML format possible (?) which makes the message nicer to read