I can say that mech really suck in TvP. I've been playing mech the whole night and lost all my matches

went from rank 6 to 12 I think. Immortals completely destroy the place unless you have at least 2 thors. I didn't use EMP in the games that actually lasted long enough so that was probably one of my weak point but honestly trying to make the ghost come to the front of your tank/thor/hellions line is hard. It's ok if you're just turtling but if you attack it's more complicated.
Also, if the Protoss goes carriers, the thor is not enough to counter so you'll need vikings. The problem is that vikings are complete crap on ground against stalkers so basically you have to do a big tech switch that will eat your money and supply without really knowing how much carriers the big push will contain.
Finally, after the great success I had with mech against zerg in the last couple of days, I was destroyed 3 times tonight by banelings rushes while trying to tech to mech. This kinda piss me off because when you scout the baneling nest, you don't have a choice, you have to go infantry. I can't even imagine trying to tech on scrapyard or any other map with an unblockable ramp. The worst is that teching to a baneling rush doesn't even put the zerg behind. It's completely ridiculous. They can do their little rush and if they don't succeed, they can safely tech to something else.