I've found sats to be extremely effective, provided you use them in combination with something else.
ex: Missle sats are useless in late game right? Wrong! 100 sats with csm's over a planet that has large weapon platforms using massive mount tachyon projection cannons is something to fear. PDC's are great, but only if they can fire!
That's just one example I'm sure some of the more experienced players can come up with more.
Nodachi