I know this trait is used for quality of, um, hospitality possible at a given town, but how exactly is it used in play?
Is it just like Wealth - "I buy a Worth 9 summer house, and spend 6 Wealth points + my Sociality to see if I get it?"

Hospitality items (lodging and food, basically) are purchased like any other item. The value for the town (like the other town values) represents the maximum value available. Thus, you may not find fine dining in a miner's camp.

I don't think there's any numerical in-game benefit to spending a lot of money on hospitality. You can be like any other standard D&D party - sleeping in the stables, swilling the foulest grog and using your 15,000 gp as a pillow.

Of course, you could also employ a modified version of one of my house rules. Basically, the more money you spent on food and lodgings, the less likely you were to be robbed (you might be attracting attention, but the better accomodations should be better-protected, and isn't your glowing +5 sword of munchkinness attracting attention aanyway?). In Donjon, I might use the level of hospitality purchased as the effective Donjon level against which a thief would have to work to rob you. This works wonderfully in reverse too - a peasant's hovel is easier for PCs to rob than the king's palace.

I think that's a great idea, Justin :)