So overall I came to the understanding that a Nav 5 should be part of the stable. Especially for the larger screen with more pixels. However, I didn't hear much about issues with the MP3/Audio function. My Nav IV is a poor performer. MP3/Nav experiences hiccups with pairing and with the sound. I use two different BT adapters and get the same stupid behaviour from the unit. Usually the "fun" start after half an hour of music with increasing interrupts until the audio simply stops. Switching the unit off/on helps for a while. I do not believe that it is just the SD card (used several types/several speeds) or the way the files are named after decreasing the bit rate with a converter. In the end it is a lot of trouble to get something such as basic as playing MP3's to work. I don't want to go through this ever again and will not accept crappy functionality from a zillion euro navigation device. Especially when it pretends to offer more functionality than many other, cheaper devices lacking this.
I have cut my losses and use it for navigation only (without voice prompts). The rest goes through an ipod/iphone remote. There is even a plus side of this; you don't have to switch pages from the Map view to Mediaplayer to skip music or search files. Not a big thing, but it is an extra distraction on top of listening to music in the first place.
So to finish my final plea is that I will install a Nav IV mount on my R80, beside already having a mount on my LC. This way I can use one unit on two bikes. In the mean time I will await the first few software updates of the Nav 5 and seriously hope to hear what owners of the new unit have to say on the (improved?) functionality in terms of Apps and Music performance. Anyone hit a snag yet with high bitrates 192+ or long file names ????? Anyone ??? Come out, come out, wherever you are!