To me, this new take on Eldar really lends to the "fast and dirty" Eldar army I want to run. The Fast Attack forces, therefore, are a big element for me and I expect to use two or three of these options in every game. Specifically Hawks, Spiders and Lancers (shining spears), but I know a lot of folks will be fielding flyers as well. So let's take a look at these swift and true warriors (through my own filtered helmet lenses).
Swooping Hawks -- I'm very pleased with the way Hawks have evolved. I rarely ever took them before because they simply weren't worth the points. If I expected to play Guard or similar light infantry and vehicle-heavy forces, they'd be quite useful, but since it seems like I've played marine-derivative armies 80% of the time, they were never expected to be very useful. But now... For one thing, like other aspects, their warrior powers have been integrated standard, so they can Skyleap as much as they like and do so without scattering. This no-scatter is huge for me because I was always afraid of landing in a bad way. Their grenade pack also got a little more useful and logical in its new details, including using a bigger blast template with more models. And their lasblasters have upgraded to three shots per turn (assault 3 from assault 2), another nice upgrade to make them more tactical. And the Exarch's sunrifle has become AP3, giving them a little anti-marine potential, though now only shoots 3 shots rather than a whopping 6. The main thing I'd liked to have seen that they lost is the old Intercept ability -- I'm thinking "Swooping Hawks can engage zooming flyers in close combat, hitting on 6s." Without Intercept they've lost some of the cool aerial combatant feel, but they're definitely better than they used to be.
Warp Spiders -- Every aspect takes one aspect of warfare and exemplifies it. The Spiders are an assassin unit, hands-down. They move like lightning across the board, pop into existence, unload a wave of razor-webbing at S6 (strangely, if the target is I3 or less it's S7) and potentially AP1 (on wound rolls of 6), and them disappear from retaliation reach n the same turn. They kill, period. Equiping your Exarch with a Spinnerete Rifle guarentees his AP1 shots, and giving him fast shot and/or marksman's eye makes him an even deadlier assassin. There is also the option of gearing the Exarch for melee combat but I think this is a mistake -- I know from past experience, he's not a combat specialist, and if used right Spiders can almost always avoid entering combat. You're best bet (IMO) is board-hopping hitmen. It's also worth noting that they are no longer jump pack infantry but jetpack infantry. The difference? Relentless for one. And it means that they can move 2d6 inches in the assault phase (which they used to anyway, they just weren't called jetpack). They're special warp jump happens in the move phase (if you choose to use it), so in one turn they can: move 6+2d6" in the Move phase; battle focus a run of upto 6" (rerollable as fleet); and then move 2d6" more in the assault phase. Crazy.
Shining Spears -- I always liked these guys but they, too, used to be so damned expensive. A unit of 5 geared out with exarch and all was about 250 points. Ridiculous. And they attracted lots of firepower as the enemy was usually smart enough to fear a jetbike squad with S6 power weapons, thus they get shot to hell before I could really make good use of them. So now they come standard with Skilled Rider (nice, especially in 6th!) and Outflank. I'm very excited about the notion of them outflanking onto the board and taking out select vehicles and monsters with their S6 laser lances. My personal vision for my unit is making some "Wild Riders of Kurnous" (fantasy wood elf unit) using customized DE Reavers -- the shining spear models are kind of static and lame. This too will be a staple unit in my new Eldar regime.
Vypers -- I used to have a vyper model. Never put it together, sold it. Kind of regretful now. The old version was definitely not worth the points, being a 50pt open-topped AV10 model that didn't even come with a weapon! Now, mostly due the the 6th ed changes like jink saves and new fast vehicle rules, you could really kit out some vypers to be fast mega-firepower. It would get kind of expensive, but say a vyper with a scatterlaser and upgraded shuriken cannon (twin-linked with laser lock rule on the SL), plus holofields becomes a mobile weapon platform with 6 S6 shots and a 4+ jink cover save at 85pts (pricey though). Make it a squadron of them and you've got fast-moving death volleys (but you're paying for them).
Crimson Hunters -- Again, I'm not a flyer player, but these guys are pretty cool. In this new 6th edition age of flyers, it's cool to have an aspect dedicated not only to flying but being a flyer hunter. They specialize in taking out enemy flyers and are equipped to do so with 2 brightlances, a pulselaser, and the Skyhunter ability which allows them to reroll to pen against flyers. I would be tempted to take one just to get rid of those pesky enemy flyers.
Hemlock Wraithfighter -- Another unique Eldar take on the flyer, this one is the F-18 of the Damned. It incorporates the ghosts of the fallen, making this a more reliable and fearsome aerial weapon. It's weaponry can be anti-personnel or anti-armor (2 blasts of distort power -- S4 AP2 that instant kill and always penetrate on 6s), along with powerful psychological warfare. All morale checks (friend or foe?) with 12" must be rerolled and it has the psychic Terrify power, which can make a unit subject to Fear from anyone you send against it. This is a very cool and very Eldar weapon -- deadly in the most unconventional ways. (Hmmm... wouldn't mind running one of these either. Aw hell, let's face it, there isn't a unit in the book I don't like!)
(Again, art stolen shamelessly from around the internet. I'm a cyber-pirate.)