Thad,

I use nothing but the 87 octane stuff and have never had a fuel related
problem (many other problems, but no fuel related ones!)

I get 18-20mpg depending on how/where I'm driving.  I am careful about
where I get it.  The little 'corner' places that don't get much business
sometimes get 'old-gas' syndrome.  There are a couple of 'big brands'
that it DOESN't like, but that may be a regional thing.  There are two
other 'big brands' that I use very regularly.  But the main difference
between brands is the additives.  For example, in the Lake Charles area,
all the biggies use a Diamond Shamrock plant to put their additives in. 
The same fuel gets used, and it gets pumped into the Exxon, Texaco,
Shell, or Diamond Shamrock's own trucks, depending on which additive got
put in.

My .02,
Tonya
87 Vanagon GL Wolfs
74 S. Beetle