Good for anyone with a well known and branded site.

Maybe so as you will get a greater share of the results pages. However, Webmaster Tools doesn't give you control over the list and also takes random title, meta descriptions, and url structures to show within these sitelinks.

I don't understand why Google gives control to webmasters for something which is very valuable information and then takes it away completely with changes such as this.

They are really a law unto them selves. It is early days though so they will probably iron it out and display the "most valuable/relavent" pages according to them. Better than a kick in the teeth though. Which they seem to deliver regurlarly and randomly as well.

That's true Nick. For all of their "user testing" and "beta launch schedules" they pride themselves on I really wonder who they actually involve within these activities.