My Thoughts on SM: (note I am only rank 7)

Hero:
I am a big fan of the Apoth, he can keep your forces in the thick of it longer, and they don't need to retreat as often to heal up. Also his abilities are really nice, his unique ones are revive all allied downed commanders from anywhere, and make all your infantry invincible for 30s (?) which for 500 red points is pretty sweet, especially if you use it to negate a orbital strike from another player since they payed 750 for it. For gear I generally take the power axe, for the power drain and plasma pistol, armor of the apothacariane, for the self insta revive, mass heal and +100 health. For equipment, generally grenades for building clearing and clumped soldiers, though sometimes the +energy / +energy regen gem if I am finding I am running out of energy before the battle ends.

Scouts:
Handy for capping, I generally keep one scout squad around with sniper to sit in the back and support as well as run around and cap / sneak up and spot.

TSM:
My army mostly consists of these guys, and they are the first units I make. The rockets are supreme against buildings and vehicles, I also take plasma for hero's and heavy inf and flamers for early Nid games.

ASM:
Effective if you use them right, this is generally my second unit out. I only take one squad though since one squad will serve the purpose you need them for, which is disruption and the melta bombs. The Sergeant AoE knockback ability is handy as well.

Dreads:
Are very effective, especially if you're a TM, for an apoth I keep my army inf only to make better use of the Angles of Death ability, and I don't like not being able to retreat them.

Preds:
Don't use them, you really need to baby sit them, and I don't find them worth the cost or effort, rather have a Dark Age Dread personally.