On Monday, March 11, 2013 5:22:15 PM UTC+1, wrote:
Do they depict US start, turnpoint and finish definitions

Sorry, I don't know US task rules. If there's anything missing, you should write a ticket (http://bugs.xcsoar.org/newticket).

tell you if you're under the top for 2 minutes

I havn't heard of that feature, but then again, I don't fly contests. (I'm just one of several XCSoar developers, I don't know every part of XCSoar)

help plan time completion for area and mat tasks

Yes for AAT, never heard of "MAT".

compute final glides to a finish cylinder with a minimum altitude

Yes.

compute final glides around additional turnpoints (mat)?

Again, don't about about MAT.

Can you input a task in less than 15 minutes?

It usually takes me a minute on my Streak.

Is there a quick task A task B option (almost all in air task changes are now A to B)?

You mean you have two active tasks, and switch between the two? No, but thanks to our excellent task engine, that would not be hard to implement. If it's really useful for contest pilots.

I tried xcsoar many years ago. Charlie Spratt changed the task in the air. 15 minutes later on my second reboot, I swore it off. Is contest task entry any easier than back then?

The task engine and the task editor have been rewritten from scratch in XCSoar 6.0. XCSoar has come a very long way since the dark 5.x days.

If not, is anyone working on a "US contest" package for either program?

No, our goal is to have everything in the "mainline". So if any US pilot decides to hack XCSoar code, please contact us for merging the new features.