Precision Airstrike and Stealth Bomber are much more dangerous in Demolition than something like TDM or Dom (though they can be useful in Dom as well for securing PITA B points). They can also be handy in HQ for the same reason, as you can all but guarantee a claim on an HQ by placing one well.
The airstrikes from the PA are different than the Harrier as well. The Harrier does two strikes that nearly overlap, the PA does three strikes, each one moving forward from where you placed the marker by a good amount. Placed correctly, they'll carpet bomb a nice big chunk of the map in a line. Because you can't control the Harrier strike direction, sometimes they'll come in at a completely useless angle, barely covering an objective. A PA never has this problem.
The Stealth Bomber carpet bombs the entire map in a line, with a much wider radius, and a guaranteed kill for anyone caught in the blast zone. Additionally, anyone indoors is dazed by the blast, making them easy prey for house hunting teammates during the strike.
I'll occasionally run PA instead of Pred, and it rarely fails to do more damage to the other team, or secure a key objective if used well.
In non objective modes, you do need either a UAV, a real team, or a recent death to place it correctly.
In general, the Bomber is less useful than a Pavelow for racking up kills, but its focused bombing can be more crucial in objective modes that are time sensitive - you need one big suppressive strike right now, not a bunch of kills over the next few minutes.
Plus, you can't shoot down a Stealth Bomber or PA, Harriers and Pavelows can (and will) be taken down with a quickness by any competent team.