[plt-scheme] printing exact rationals

On Jul 9, 2009, at 14:06, John Clements wrote:
> On Jul 4, 2009, at 5:32 AM, Robby Findler wrote:
> If you right-click on the number and choose a different format, that
>> choice will be remembered for future printing.
>
> Along these lines, Ian pointed out to me this week that for the  
> printout of rationals in decimal format, you can click on the "..."  
> to get another chunk of digits.  This is incredibly nifty, but I  
> would never have figured it out by myself.

What do you call something that's cooler than an easter egg, and  
actually useful?
What else don't I know about DrScheme [...] ... ?