I agreed the RNS 510 sat nav cost ridiculous amount of money but my job involves visiting a lot of unfamiliar place in a short space of time. Its a no brainer for me. I find the unit reasonablely accurate when compare with a Porsche PCM 3. The fact you enter the postcode via touchscreen is miles better than an Audi, Merc or BMW. As mention above, there are occasions when the unit let you down but you will find the portable ones which I also bring along to work also struggle to find those addresses! Just like xenons, depends on what you use the GTI for, it a total waste of money to one but absolute must for others!