One of two reasons I began playing Eldar (second is how cool their tanks look). Fluff-wise all aspect warriors are so freakin' cool I could play using only them if that were possible. Well... It is possible. Is it worth it? Let's find out.
That messy picture above is my workstation with models I'm currently working on. As you can see, there are only aspect warriors, nothing else. Of course in my army there are some other units, but aspects form at least half of the list.
Let's begin with troops. In this section we have only one aspect unit. Dire Avengers are IMO the best troop choice in Craftworlds army. Not very expensive, with a bit better range than Guardians, better overwarch and some cool options for Exarch (Bladestorm!). If you are seriously thinking about Eldar army, get at least one box of them. I just bought my fourth set, but I think I'll get another three, to fill my second battalion, if I ever need to field two battalions.
Then we have elites. Generally speaking Eldar elites are everything but elites. If that section of codex disappeared most competitive players wouldn't even notice.
Fire Dragons look nice on paper, but when you try to field them you'll see that they are very expensive, die easily and have a weapon that has short range and only one shot per model. Of course, S8, AP-4 and D6 damage looks fine, but in Eldar army there are loads of units that can deliver this kind of punishment without dying from few bolter shots.
Howling Banshees do one thing well, and that's shutting down overwatch. Enemy cannot fire overwatch against them, and after they are in combat, rest of your units can charge without fear of, say, heavy flamers. For 55pts per unit I think one squad may be good, if you are planning on using many close combat warriors, which I don't recommend. All in all, you can buy and use them (expecially after new sculpts became available) but Banshees aren't first, second or even third pick while building an army.
Striking Scorpions are highly underrated aspect warriors. As a matter of fact I'm planning to get a unit or two. First cool thing is their Exarch, who is quite a killer with his claw. They also can deliver some mortal wounds, and appear via deep strike, which makes them excelent objective grabbers. Not first, but maybe second choice IMO, but if you asked somebody else, they'd probably say "don't use Scorpions!".
Fast attack section has three aspect units. The worst of them are Warp Spiders. Problem with them is that they are quite easy to killand their weapons are less effective than weapons of other unit for the same points.
Swooping Hawks are much bettrer. Fast, with ability to deep strike and then go back to reserves, way to deliver mortal wounds and gazzilion of shots. Of course those shots aren't very powerfull, but sheer number of dice should do something, expecially if you are targeting GEQ's or something like that.
Last but not least, Shining Spears. They have only one flaw. Official models are ugly. Good thing is, it's quite easy to convert Windriders into Shining Spears. Those aspect warriors are very fast and hard hitting unit. If you doom + jinx their target, chances of survival for that enemy are quite thin. Get at least one unit of 8 + Exarch (of course give that Exarch Star Lance). I even think about building second and third unit, giving me an option to field three maxed units. Probably I won't do it, as I prefer Eldar being highly mobile and shooty, but army based on three huge units of spears would do some serious damage.
In heavy support there is only one aspect unit, but what an unit that is! Dark Reapers are very powerfull long ranged warriors, with very important rule that make them shoot on 3+ no matter what. Exarch may take Aeldari Missile Launcher or Tempest Launcher. The later is very nice, as it allows Exarch to fire indirectly. Get yourself 3 boxes, and build two three-model squads and one nine-model, that's IMO the best way. Reapers and Shining Spears are the best aspect units, for now at least.
The last (but not least) aspect warrior is quite a big one. Crimson Hunter is quite a nice plane, which can be used... If you need 6 planes in your list. If not, use up to three Crimson Hunter Exarchs. Their cost is simmilar, but the things CHE can do are way more destructive to your oponent. Currently he can get either 5++ save (Evade) or ignore move penalty while shooting (Hawkeye). Both are very good, I usually use Hawkeye, but Evade is also good.
Well, that's it. All Aspect Warriors (from codex, no FW entries, as those are unreliable as hell.
Let me go back to painting, I'll post some pictures soon :)