As of today, exam 70-663 is now available to take at your local Prometic test centre. After passing 70-662, TS: Exchange 2010, Configuring this is the only exam you need to pass to become MCITP on Exchange 2010.
As someone lucky enough to take and pass the beta exam (they cancelled a LOT of places – thankfully I booked mine for Dec 1st) I can say it’s certainly no harder than the Exchange 2007 MCITP exams. If you have already passed those, although there is not a specific upgrade path you won’t be too dissapointed as much of the same ground is covered apart from new features, like DAG, RBAC etc.
One area where I am disappointed with the MCITP in general is that they aren’t hard enough. I’m not likely to win any friends by saying that, but personally I want to feel really satified after passing the exam. With exams like the VCP getting harder I think Microsoft should follow this example and make the MCITP something that is hard to achieve; there simply is too much of a gap between MCITP and MCM/MCA and too little of a difference in skill level between MCTS and MCITP.