Just wondered as I will be travelling in Europe and will load a few POI files..as my gps unit is quite old nuvi 250...does it cause any performance issues?
The technical answer is "yes" it will slow down the redraw, but will it be enough for you to notice? Not likely, unless you have several icon files clumped close together, like several restaurants in a row, but even then, I doubt you'll notice it.
The amount of memory in the GPS is far more than it needs to do it's job. The contents of the files are primarily text (ASCII) information. The amount of memory a text file takes up is very small in comparison - so you should be able to put thousands of POI points into the system w/o a slow down.
One thing you might consider doing is removing from your unit (deleting) all the voices and help files in languages you don't use. I did so and it freed up a substantial amount of room (memory). You can always reload them later if you want to. I have almost 30,000 extra POI's loaded and don't notice much difference in speed.
The poi loader combines all of the poi files in the source directory into a .gpi file. This .gpi file is either loaded directly into your GPS, or you can put it onto an SD card and load the file manually from the SD card, but the GPS will delete all the previous custom poi locations when it imports the new file, so if you wish to keep all your old poi's, you have to make sure that the csv or gpx files for all your old locations are in the one folder along with all the new locations.