Thank you for a most informative post.
I would like to make one comment though, which I think is very true for Sins, but also from my experience with other RTSs over the years is a good advice for a lot of RTSs.
Players tend to neglect spying on their opponent. If you don't have good intel on your enemy, you don't know what he is up to. And when he deploys his strategy there are two options: 1) You did the right thing to counter him without knowing by chance, or 2) you are caught by surprise and you loose. #2 is more likely to happen than #1, and in either case it's not a good idea to leave this to chance. Two players that don't spy on each other are basically just playing a very long game of rock-paper-scissors.
For example, if you opponent uses LR spam and you go for HC spam - if he attacks early enough you loose. On the other hand if you do LR spam and your opponent goes for HC, you must attack early, because once he has enough HCs, he will overtake you in military strength. You can spot the difference between HC and LR fairly early on in the game by the number of military labs your opponent builds.
It's also very important to know where your opponent's main fleet is. If he is moving a large number of ships, then he is up to something. Try to infer from the movement what he is about to do and react appropriately. This is VERY important in games that have two choke points - you can't effectively defend both routes statically, so you must have enough advanc warning before your opponent attacks. I often like to attack my opponent when his main fleet is on the move - if he retreats to defend then I screwed up his plan and I have a little time to chew his defences before he arrives. If he let's me have the planet and moves on with his plan they I got a head start on him in terms of aggression. In either way you can know exactly what he thinks in a second if you've got "eyes" all over his territory - the second his ships turn around you know it.
Do not rely on the "Radar" technologies alone for intel. In level 1 they only warn you once your opponent launches his attack, which is most probably to late. In level 2 they are more effective but still produce a lot of false alarms. In either case it's not enough to really know what the other guy is thinking.There is not replacement for sending scouts into enemy territory and having "eyes" there.
Scouts are cheap, fast and effective. Do not neglect them, they are worth much more then you pay for them.
One of the things I like about Sins is the fact that there is a little depth to the intel war. The 3 races have slightly different means of spying on their enemy, and you can try and "blind" you opponent by taking out his scouts (although that's rarely successful).
That's it. I hope that will help some of you guys to beat the shit out of me next time around...
Thanks again for the very helpful post.