Parameter usage highlighting (part 2)

Ok.  As promised, here's a picture of the feature in action:


So here's a bit of code of mine.  It's specific purpose is to
convert a Generalized Nondeterministic Finite Automata into a Regular
Expression.  Now, this code is basically a port of an algorithm in
the book Introduction to the Theory of Computation
by Sipser.  As such i've tried to keep the names and structure
very similar to his so that it's easy to refer back to the text and
understand what's going on.  Unfortuantely, in the algorithm dummy
mathematical throw-away variables (like Qi and Qj)
are used, and when you translate that to code you tend to find it
difficult to distinguish individual variables in the density of the
surrounding code.  

However, with this feature it suddendly becomes a lot easier.  You
simply place your identifier on the variable in question and very
quickly afterwords two things happen.  The first is that the
variable you are on gets surrounded by a small dotted rectangle. 
This allows you to distinguish what the declaration is and what the
references are very easily and it also helps a user understand what's
going on the first time this appears (in case they just moved their
cursor to a location while navigating around and are suddenly alarmed
by the highlights that pop up).  The second is that all references
to that variable show up highlighted in your source.  Now i can
very simply scan the code and ensure that i'm using this variable
properly.  Without this feature i would most likely get confused
between qi and qj as i flipped back and forth from the code to the

Now that you've seen it, is there anything you would like changed about
it?  Or do you think the feature as is would be a useful thing?