The C&C community manager, Aaron "Apoc" Kaufman, paid a visit to community forums after returning from the Leipzig convention. This is what he posted on the official boards: The Game Speed
Our notion for this game is "fast, fluid, and fun". The speed of all the units is not set in stone right now and that will come with balance, but ultimately, it will be faster paced. Everyone who saw the game in person loved the speed, but certainly, we're very early, so the speed is definitely something we will be tweaking up until the last moment. Building Speed
Impossible to judge this, was for demo purposes only. The buildings will build instantly, but it is their BUILD TIMERS which will determine when you can place it down. The main goal here is, we didn't want the opposing player's building to be attacked while it was building, takes away from the strategic and fast paced gameplay. Don't forget though, you may be building an Obelisk of Light, but if the timer isn't done and you loose your power, sionora. Point here is, building speed is all balance and we've barely just started touching balance, don't judge the demo on this balance aspect. The Lifetime of the Buildings
Same as above, for demo purposes only we sped things up, this will definitely be balanced. The goal of a demo in a short amount of time, quite literally, show us the cool stuff. The lifetime of the buildings is definitely not realistic in the video but for the purpose of time and demo, we had to get thru everything quickly. Walls, Gates, And Defence
The answer here is simple, C&C 3 will have walls but they were not ready for this demo, so no worries, I think that answers your fears there.
Bottom line on these concerns, they are 100% fair based on the video, but let me reiterate:
The demo is not accurately balanced but its more about the visual presentation and showing the gameplay elements. So, yea, Stealth Tanks are good to destroy a power plant, Vertigo Bombers take out tanks, Mammoth Tanks are incredibly powerful and can level a base that isn't properly protected. We have barely touched balance, so no worries, we will be tuning balance and speed very intensely thru development.
You haven't seen all the GDI and Nod units, far from it, and that's all I'm going to comment there right now.
The intent of the demo was to showcase what a slice of C&C 3 action can look like, and remember guys, we're still very early, there is TONS that has yet to be revealed. Take the video for a visual representation of the gameplay, not a specific balance assessment.