1) Since we know nothing about it currently, how does the Nydus Worm mechanic work?
First you build a Nydus Network, and load the Network with all your ground units. You can then spawn the Worm at any location as long as its on top of creep (including enemy creep). Once the worm emerges, you can either unload or load units.
2) How effective did you find the viking and reaper when playing terran?
I found the Viking extremely effective. Such an amazing unit at destroying resource lines and air units. You can easily dodge ATA units by turning into a ground unit, and on top of that you can go to air to dodge GTG units. The Reaper I only found useful with D8 charges, but it requires an upgrade and is late tech, so I think it needs work.
3) Have there been any changes to the ultralisk, and did you get to play them and test how effective they are?
Unbelievably effective. For fun I massed 15 Archons (I have a screenshot) against my friends 4 Ultralisks. He nearly took out half of my army, and that was without the Cleave ability. They are deadly unless you have high damage output units or disablers like Graviton Beam.
4) What happens when you merge different templars together?
Nothing. You get the same basic Archon no matter what combo of templars you use.
5) Did the two Dark Templar models bother you during gameplay?
Not at all. You dont even notice it in the least bit unless you literally stare at the screen and zoom in. It doesn't affect gameplay at all, I mean seriously, how can you NOT TELL its a DT.
6) Was the prediction that ZvZ is primarily "Roach vs. Roach" combat correct?
Rarely did I see a Roach vs Roach match up. You would see Roaches, but I would see more people tech up to Mutalisks more so.
7) What do you think about Xel'Naga Watch Towers? Do they make that much difference, since we heard Dustin Browder saying that controlling them can be a key to victory in BR3.
I believe they do. Every game I played I would secure at least one tower using a Marine. This extended site can help you determine where the enemy army is heading, or where there expansion will be.
8) What do you think of the new resourcing mechanics? Is it annoying to have to reclick the proton charge for probes and remember to call down new mules etc?
Annoying? You mean you'd rather have the game play for you? No its not annoying, it keeps you on your toes and attempts to increase some macro. But no I find it great, especially the Proton Charge. Its one of those abilities that I would usually try and tech to as fast as possible because the extra income is helpful.
9) How do you think spawn larva compared to the Protoss and Terran macro mechanics?
Some say its "weak" and "uninspired" compared to the other races, but I would have to disagree. The larva are permanent, which is basically like 4 extra drones each time its used, and on top of that its also helpful if you need extra drones to build structures.
10) Are destructible rocks passable by any other means than air or destroying them, example pylon next to them so you can warp in units on the other side?
Yes you would be able to warp in on the other side, but thats about it. Even Colossus and burrowed Infestors are unable to pass under/over destructible rocks.