[postgis-users] Is postgis the right tool for this?

[snacktime]

I'm very new to GIS, but we use postgresql extensively so postgis
naturally came to mind when we landed this project.

We need to create a nearest neighbor search feature.  The search will
be for doctors within a certain radius measured by miles.  The
database of doctors is right at 1 million.  Whether the search wll be
within the radius of a specific street address or just a city is
unknown at this time.  If compiling a complete US street address
database with latitude and longitude isn't too much work we will do
that, but if that proves unworkable we will probably just fall back to
searching the radius of a city.

I've read over some of the postgis documentation, and it appears that
the Distance function would do what we need.  I also saw a post on
this list that suggested postgis might not be well suited to what we
need, so I'm looking for some confirmation on if postgis is or is not
a suitable tool for our situation.