This is an incredible tomato salad but there are two things to remember if you want to wow your guests with something so simple. The first is that you should try to get a mixture of different, tasty, local (if possible) tomatoes in all different shapes, sizes and colors. Second, the flavor is brought out by salting the tomatoes, so don't skip this bit. Some people get worried about putting this much salt on their food, but the bulk of it will drip off, leaving you with really beautiful, intensely flavored tomatoes.
If you can get hold of some dried flowering oregano then do, as it has the most heavenly flavor. Feel free to use the dried stuff that you get in a little container, but it can taste a bit like sawdust when compared to the fruity, fragrant flavor you get from the flowering variety. Oregano is also great to grow in the garden.