Thought I'd take my own shot at this ... 5 beers means big big trouble, use your spellbreakers here!
Before I joined the proper ranks of the good Dwarfs, I played High Elves. I repeatedly destroyed Dwarf armies behind the power of the Lore of Shadow. This is a lore with 2 game breaking spells and those 2 spells alone are enough. A High Elf Archmage with Seer should be using this lore against Dwarfs. A Lizardmen Slann should be rolling at least one Shadow spell, more if he rolls 5 or 6. Others with access to the Lore (Demons, Hordes of Chaos, Dark Elves, Empire) can seriously consider it, although normal rolling for spells makes Lore of Shadows a lot chancier.
Steed of Shadows - 2 beers

Oddly, the value of this spell is less changed by the tactical situation than by the army list your opponent brings. If they have a character they are willing to fling around all alone, this is a good spell. If they don't, its largely worthless. For example, Lizardmen inevitably have a Saurus character to fly at you, but Empire usually doesn't want to fling a hero around (and most of them are mounted anyway, and thus not usable).
The main threat of this spell is early turn charges into our war machines. It still matters in later turns, but usually only in support of something else. Also notice the range of the spell - 12 inches from caster to target.
To protect a war machine on one of the first couple of turns, this is definitely worth using dispel dice against. It is probably not worth a scroll, but that depends upon the enemy's other spells. Also note that most heroes have only 3 or 4 attacks and our war machines often have 4 crew. A hero is not likely to wipe out a war machine crew in one round, giving us the opportunity to stubbornly hold, charge him with an infantry block, and destroy him. Trading a war machine for an enemy hero is sometimes a good trade.
Its other significant use (late game) is to pull a wizard out of close combat. Most wizards are quite squishy in close combat so killing the wizard (and gaining the combat resolution for doing so) is probably more important than stopping whatever else the enemy might cast. In that situation, it is absolutely worth using dice to stop. If you still have a spellbreaker that late in the game, it is probably worth using as having kept it that long indicates there isn't much need for the spellbreaker otherwise.
Creeping Death - 1 beer

A decent spell against heavy cavalry, especially Empire knights. But we are Dwarfs. This spell needs to roll above average to kill even 2 Dwarfs. Ignore it.
Crown of Taidron - 0 beers

The only spell in the 8 main lores I give a 0. I have never cast it, seen it cast, nor met anyone in person that has used it effectively. Especially with our Toughness 4, this is likely to do as much damage to the caster's side as to ours. Even in an ideal situation where it will hit only one unit from the caster's side, d6 hits won't hurt us much.
Shades of Death - 1 beer or 4

With Dwarf leadership, making an enemy unit cause fear or terror is not that serious. Or at least is less threatening that other spells. However, once combat starts, this spell creates the potential to bypass our resistance to breaking by causing a fear autobreak. If an enemy wizard knows this spell, you must pay attention to any combats that happen near the wizard. If you are outnumbered and might lose, you need to stop this spell.
Unseen Lurker - 4 beers

Magical movement is a potential game winner. Lurker's big limitation is 12 inch range from caster to target, so arranging flank charges with Unseen Lurker is not so easy. Of course, if they can arrange a flank charge with it, we are really in trouble. Except for the casting range, this is the best magical movement spell, since it lets the target make a FULL MOVE. That means 20 inch fly charges or heavy cavalry going an extra 14-16. This produces easy turn 1 charges into our shooting units or war machines, potentially meaning they never take a shot before being killed. Another late game tactical use is taking a unit we broke the previous turn, but has just rallied, and Lurkering it back into us immediately. Extremely effective when used on heavy cavalry, chariots and other things that really like to charge.
Unseen Lurker is a spell to save spellbreakers for, unless you've had to use them on ...
Pit of Shades - 5 beers

The ultimate spell for directly removing Dwarfs from the table. Cast on a normal Dwarf block of 20-25, it likely kills 2/3 of the unit in one cast. Or it instantly destroys a war machine because initiative 0 means auto-fail. This is where your spellbreakers get used.
Edited by Lord Firmshaft, 04 August 2008 - 10:50 AM.