Just to add to this list, I have been using Postgresql to store data
for multiple GPS applications handling more than 150-200 vehicles.
Some of the tables that I have are running into 20 - 25 million rows
at the max, and on average 10 million rows. I am yet to see a problem
from the database side, although must admit that I receive data every
10 seconds from the devices.
I am sure that optimizing the postgresql.conf files, and using postgis
would be of great help down the road.
With regards
Amitabh