For those of you who are ready to bury the hatchet and move on, there is a very nice GSAK macro available that allows you to pull data from opencaching.com into your GSAK database. It is called OpencachingGarmin.gsk, and was written by one of my favorite macro developers, "hynr".
The macro works great and runs quickly. By default, it will use your designated home location and pull all the caches within a specified grid into the GSAK database of your choice. You can modify any of these input variables, including the number of caches that you download from the site:
If you load the OpenCaching caches into the same GSAK database containing your geocaching.com caches, you can distinguish between the two by the Code name: geocaching.com caches begin with "GC", whereas opencaching.com caches begin with "OX". In addition, opencaching.com caches do not contain the State location, so in the GSAK State field they will be listed as, "Nil". Once you have all the caches you want from both services in GSAK, you simply load them all onto your GPSr as you normally would (see this help file), and you're good to go.