<p>I currently have an MS Access application that connects to a PostgreSQL database via ODBC. This successfully runs on a LAN with 20 users (each running their own version of Access). Now I am thinking through some disaster recovery scenarios, and it seems that a quick and easy method of protecting the data is to use <a href="http://www.postgresql.org/docs/8.3/static/warm-standby.html" rel="noreferrer">log shipping</a> to create a warm-standby. </p>

<p>This lead me to think about putting this warm-standby at a remote location, but then I have the question:</p>

<p><strong>Is Access connecting to a remote database via ODBC usable?</strong> 
I.e. the remote database is maybe in the same country with ok ping times and I have a 1mbit SDSL line.</p>

Yes.
I don't have any experience using Access to hit PostgreSQL from a remote location but I have successfully used Access as a front-end to SQL Server & DB2 from a remote location with success.
Ironically, what you don't want to do is use Access to front-end an Access database (mdb) from a remote location over a high-latency link.  Since hitting the MDB uses file-based operations it's pretty easy to end up with a corrupt database if you have anything more than a trivial db.