Chaplain Stephen said:
:x IMHO the orbital strike is damn near useless. Being limited to one piece of terrain just limits it entirely too much.
Not at all, really. The biggest part of the thing is to key it to the right terrain. Picking that bush stuffed way off in a corner? Yeah, dumb plan. Picking the ruined building just out ahead of his deployment zone, the one his whole force has to pass by? Real potential to cause tons of damage. Thinking ahead about where he's likely to deploy any particularly juicy targets (say, a guard player with a few Basilisks) can also help you make the strike count.
Handy (if slightly cruel) trick: Roads/Rivers/etc..
do count as a single piece of terrain, so you can plot the strike to the road down the middle of the table and drop your shots at any location along the whole length of the road!

:tongue:
Then there's the matter of the scatter. While it makes it less than reliable to hit specific targets, that same scatter means that anything within 12 inches of that terrain in any direction could potentially have a big heap of Ordinance Barrage pain coming their way at any time. That's more than 3 square feet of tabletop under constant threat.
Finally, you are
not required to tell your opponent what terrain you've picked. Write it down, and keep it secret until you start dropping templates. Even just the knowledge that he could be facing S10 AP1 pieplates o' doom dropping near any terrain you choose can put any opponent seriously on edge.
How has it worked for me? Hit and miss, really. Some games it just pulverizes empty fields. Usually it will get some partial hits on a few units, maybe a weak hit on a tank, just enough to cause some chaos. Occasionally, it really rocks. I've seen it Vaporize a Vindicator, Destroy a Dreadnought, and Terminate a full Termie squad all in one game before. (Sorry for the corny alliteration, everybody... <_< ) In short, if you pick a good terrain piece, try to keep his troops stuck in the kill zone if possible, and get some lucky scatter rolls, they can be devastating. (or they can be useless. Nature of the beast, really...)