Performance Expectations

Hello all,

We're using PostgresQL with a fairly large database (about 2GB).  I have one
table that currently exceeds 4.5 million records and will probably grow to
well over 5 fairly soon.  The searching of this table is basically done on
one field, which field I have set up a btree index on.  My question is, if I
search this table and get the results back in about 6-7 seconds is that
pretty good, not so good...?  What are the things I should look at in
determining the performance on this?

BTW, forgive the lack of information.  I'd be happy to post more info on the
table, hardware, etc.  I just didn't want to overwhelm the initial question.

Thanks,
Derek Hamilton