We digress, but since it's your topic those are all personal reasons, which I somewhat disagree with, from personal experience.
Diesel isn't hard to get. I've only ever been to two stations in two years that haven't had it. And infact, one had it but it was a hi-flow pump for trucks, so I couldn't use it. I've done over 65,000km in those 2yrs so I've seen my fair share of stations.
Also the price of diesel is much more stable. Apart from the crazy, insane prices we had in mid to late 2008, I've never paid more or less than $1.2X per litre.
The initial cost is also something that comes down to a personal reason i.e. usage. If you do many km's as I do, you quickly recoupe the costs in the efficency, not to mention that the cost is usually reflected in the sale prices, when the car would be on-sold. The few thousand more that you bought it for, over a petrol equivalent, would also be a few thousand-ish more when you sell it.