Which POIs have you added out of interest and what was the source?
Just the Tesco Fuel one at the moment (as I use their Momentum 99 in my R). Got them from http://www.pocketgpsworld.com/modules.php?name=POIs as they have lots of free ones. Was also thinking of subscribing to the Speed Camera Database but that costs £20 per year.
I subscribe to the speed camera database and find it a worthwhile addition to the satnavs capability, but with qualifications!
Although you can load POIs via car-net, I have yet to find a method of enabling the sound signal, when approaching one of these POIs. Adding the POIs via an SD card, and the German VW satnav website, does offer this facility, which is an obvious necessity for speed cameras. However, here comes the qualification, the sound signal is not the ideal strident squawk and only gives around 30 metres warning.
Unless you are a serial, extreme speeder, I think having the camera sites on screen is still really useful, if only to illustrate just how many potential sites there are, these days!
I have my screen on a fixed scale of 300 yards, which shows camera sites for a useful distance ahead. An occasional, careful, glance at the screen, or getting your passenger to monitor it, allows you to "make progress" safely enough.
Details of how to get suitably prepared POIs onto an SD card can be found
here. The German Satnav Companion website has since moved and can now be found
here. Note that, although reference is made to Discover Pro, this also works for the standard Discover Nav.
HTH