I've been giving some thought/brainstorming to the missile changes and how they'll effect tactics.
For missiles themselves, ECCM is probably the easiest to analyze. Basically it becomes worth it if your warhead size x the accuracy improvement >= .25 MSP. For the basic reasoning that having x% more missiles hit is pretty similar to having missiles do x% more damage (not exactly similar, but close). Assuming 1-2 MSP warheads, this probably means that level 1 or 2 ECCM wont be very useful; after all, you wont be sure if the enemy will have ECM. 3 becomes quite worthwhile if you expect the enemy to use ECM, and beyond that I suspect it will almost always be worthwhile.
Missile ECM is more complicated, and probably a bit of a nerf to AMMs; after all, it doesn't take much to link ECCM to fire controls, but I doubt you'll put ECCM on your anti-missiles until very high tech levels. I consider this a good thing; currently AMMs are extremely capable and often result in 100% destruction of enemy missiles, turning them into something that thins but doesn't stop incoming waves is a positive in my book. Also they currently become progressively better against equal tech missiles as you advance; giving them a scaling penalty with higher tech will help balance that out. For that reason I think missile ECM will be quite powerful; you might not be able to rely on it against beam PD, but avoiding AMMs (or forcing your opponent to add ECCM to their AMMs, which is a net gain for the larger missile) is quite valuable.
