Wow - so much negativity and conjecture from people who are, if you don't mind my saying so, unlikely to have a clue what they are talking about.
It's not easy or wise to just guess how structurally sound something is by just looking at it, as it's quite likely you'll come to the wrong conclusion. As this a replacement for their best selling bike, so probably extremely important to them, I think I'd trust Planet X to have got this right.
I confess, I have two bikes from Planet X that I've been extremely happy with, so I'm probably a little biased. One of them is an old Pro Carbon, which to my eye is even more compact than the new version, and mine (I'm 6'4 on a bike with 56cm seat tube) probably has more seat tube showing than the one pictured above - it hasn't broken. Actually, I think it's rare to hear of Pro Carbons breaking, and there seem to be plenty of them out there.
I think it's a fantastic looking bike and disappointingly for all the people that love to hate Planet X, it'll probably have the performance to match.