I'll agree with DK that Light really only shines (haha) when you use it in a Coven. Especially with Allie and her "Flag of +4 Bubbles". The fact is that Banishment with a Coven is the most reliable option for hard-hitting in the game, the Sig-spell competes perfectly with any other Direct-Damage sigs (plus the option to be vicious against certain targets), and being able to bubble-out your spells with a massive casting bonus is awesome.
That said, I'm not the biggest fan of Light Covens. That's not to say that they aren't ah-mazing, but I don't think that you get a very good return on your investment - with or (especially) without Allie. On the table, most of your casting phase with a Light Coven comes down to spamming the damage spells. Banishment is there for wrecking an opponent's tougher units, but you're normally multi-casting Burning Gaze more than anything.
The catch-22 is that once you've sunk points into the Coven, you're usually not going to have points free for multiple units worthy of the buffs. The Coven will usually get dumped into a single regiment, as there's a need to protect the "squishies" (notably: Allie and her BSB will only have a 5+ Ward, and little/no armor) and you want to keep all of your Wizards close. Usually you end up with a Deathstar. This usually means White Lions if you have Allie and her 5+ Ward, or Phoenix Guard if you don't. The problem with the Phoenix Guard is that they need the Razor Banner if they want to kill anything, but you really want the Banner of the World Dragon so that you don't blow up your Wizards and half your unit every time you Miscast.
So in the end, a Light Star is about using Magic to make up for our otherwise terrible ranged-combat abilities, and then 1D6-buffing a single regiment with all the good stuff and just hammering it into the enemy. It's a very powerful army, but it's very one-dimensional, and Daemon players would rather slit their own throats with a rusty spoon than ever play against you.
Otherwise, Light isn't a hideous Lore for elves, but it doesn't add much beyond what you've said: the movement buffs. And it gets very expensive when you start trying to bubble the spells out. You're right though - the only spells that you're really looking for are probably Speed of Light and Timewarp, maybe Net. The Sig doesn't really help you out, if you get something that you don't want all you'll end up grabbing is a Magic Missile. It's in the same boat as High Magic, really (worth mentioning: High Magic can give you a huge movement boost) - you want about 50% of the spells, and everything else is either situational or worthless. Would be great if you could choose your spells or be a Loremaster, but we can't exactly do that.
I've said before that Magic isn't something that you should plan a strategy around. Look at your army, determine what you need, and see if you can get it from your armybook first. If you want a mobile "pick your battles" type of army, then you might want to start fielding a lot more Cavalry. I've run an all-Cav army and had great success with it, although it does require some different thinking to get the most of it. I will stand by the fact that High Elves are one of the 4 armies in the game that can do an "all cav" army (also Dark Elves, Empire, Brets).
When I pick a Lore of Magic, I look at a few things:
1) How many spells from the lore do I want?
2) How do these spells make my army better?
3) How good is the Sig Spell (for the spells I don't want)
4) How hard are these spells to cast?
In that order.
My favorite "Elf Lores" (this includes Dark Elves) are Shadow, Metal, and Death. The reasons are simple-
:: Shadow makes S3/T3 Elves a problem for my enemy, rather than a problem for me. The only spells that I will not want are Pit, Pendulum, and Steed. And of those three spells, Pit/Pendulum are actually useful at times. The Sig is also amazing. Every time I field a L4 Shadow, I end up with the sig spell, and don't mind.
:: Metal lets me deal with armor. It also gives me an almost 100% "turn over" on my Attacks-to-Hits ratios, since most Elves will be hitting on a 2+ and quite a few get rerolls. On the whole, it's a lot more situational than Shadows, which bothers me. You can use Shadow to overcome Armor by making it much easier to inflict wounds (or just casting Okkam's, if you're lucky). Metal however, will deal with one of the biggest problems that Elves will face - foes with heavy armor. Being able to cook Chaos Warriors alive when they're one of the only things that can deal with White Lions head-on, is awesome. Metal even has a good anti-horde spell, basically guaranteed to kill off 33% of whatever you cast it at, and it can "auto-pop" characters inside the unit. A lot of people also really under-estimate Golden Hounds as well, because they forget that if the character passes his Look Out Sir rolls, the hits are commuted to the unit around him. So you can target their character, and then kill a huge chunk of their unit instead - whereas most character-sniping spells will either wound the Character, or do nothing.
:: Death isn't as popular an option for High Elves, but I love it. High Elves have great leadership, but we're not good at handling challenges. Death gives us a slew of awesome character-sniper spells, and the Sig actually keys off of Leadership. SoulBlight isn't as good as Withering/Enfeebling, but it combines both effects into a single spell, and is well worth the casting value (and is bubble-able). The real shine however, is Doom and Darkness. Elves have a tough time beating Steadfast, but Doom just straight ignores that. I picked this lore up after someone else Doomed my White Lions and sent them packing from combat. In my last game, Doom would have won me the game on T3 (was using my Warriors, but still). Purple-Sun is really hard to cast, but it hangs over your opponent's head like a guillotine blade. Even against I3 armies, you're going to kill off 50% of whatever regiments it touches. It is the most reliable of all the similar spells (Dwellers, Final Trans) when it comes to killing huge swathes of enemy units. Better still, there are 4 armies in the game who will simply walk away from the table when you cast this; Dwarfs, either Undead, and Ogres. If you have a Shadows caster on the table, Death becomes the most broken lore in the game.