'nearby' means ordering your query using the <-> operator.
'meeting criteria' goes in the where clause.
For example to find interesting things nearby in postgres:
SELECT * from interesting_things as it where (it.A ='A' AND it.B ='B' AND it.C = 'C')
order by it.location <-> point '(current_lat,current_lon)' LIMIT 10
http://wiki.postgresql.org/wiki/Whats_new_in_PostgreSQL_9.1#...Sure, Postgres works great and it's not our competition. The idea is that you'll store all of your static stuff in Postgres, and all of your dynamic objects in SpaceBase. We've been approached by companies that need to track thousands of vehicles, each updating its location every second or so, and Postgres just couldn't handle it. For LBSs, SpaceBase complements Postgres.
Do you have a trial? Or other demo? I may be encountering those kinds of problems in the near future and would like to see whats out there. Right now Postgres is perfect for our workload but we've crafted the problem we're solving to avoid the realtime issue.
Extremely high spatial ingest rates concurrent with queries requires different architecture and algorithms.