I am using this software with an iBook G4 running 10.5.2 connected to a Garmin Nuvi 200.

It works fine but, there is still a bug with the mph/kph conversion.
When you load POI with a proximity alert and want to set a speed limit to trigger the alert, the value you enter (or the automatically set value if you are not using the "Manual" mode) is understood as mph even if you have choosen "Meters and km/h" in the UI.

So it you enter a POI with a speed limit of 110 km/h it will be stored in the Gramin device with the value 177 km/h. (110 mph)

Same thing for the distance trigger for proximity alerts, which seems to be the speed times 10.

So a speed limit of 110km/h will be stored as 177km/h and/or 1770m distance alert.

If soemebody knows how to contact Garmin mac dev team, the support page of their website is not working and it is not possible to send them an email throug the site.

Tip: Once the 2.0.2.1 beta is installed on you machine, you cannot rollback to the official version (2.0.1) because "a newest version of the software is already installed"
But with Pacifist you will be able to extract the POI Loader App from the installer and replace this beta version