Im not going to get right in to the whole main dealer thing, but many exploit the fact that consumers trust them too much. There are many great main dealers out there, but sadly there are too many rip off ones too. Anyway, back to the tyres... there is no safety issue provided the tyre stays inflated. That being said, it would be the same for any car really. The main advantage of a run flat is you dont have to change the wheel and there for avoid the weight and space penalty of carrying a spare and tools etc. (Although I do argue the culmative additional weight of the 4 run flats as an unsprung weight can't be far off that of a well designed spare wheel and tools!) Another concideration is the tyre pressure, a run flat has a more solid tyre wall so the pressure you run a normal tyre at may need to be addressed, and also check for any uneaven tyre wear that may result from this. What tyres you thinking of going for?