I have had a proper read through this now. Here are my thoughts.
Im pretty sure at best the Eldar are the worst 6th ed codex. Perhaps even worse than Chaos marines in terms of useful units.
HQs
Farseer and Spiritseers are the only decent HQs. Pretty much all the special characters are over priced. All the relics are rubbish, beyond some possible uses for the wing thing that allows a super run.
Avatar is over costed and nothing special. Greater daemons without wings are a bad idea. Autarch is kind of okay, nothing spectacular. He will die horribly vs any proper melee Lord. The only real use I can see is give him a jetbike and either a fusion gun or a reaper launcher.
Warlocks I kind of like. Since you get free powers and don't need to pay for them. However you do have to cast them now. On fairly shoddy leadership.
Ancient doom is kind of poor. How many slaanesh armeis are out there? Battle focus is possibly good, possibly average. Its certainly not bad.
The Warlord chart is bad. Absolutely nothing stands out as good. A lot of it is lame.
Troops
Dire Avengers are MORE expensive, despite being worse. No the false rending on the guns is not great. If they had their ability to increase rate of fire as well, then maybe they might be acceptable. I suppose the clue is in the name.
Guardians. Well they got better BS and WS and I think Initiative. They did not get Tau fire warrior better, and they cost the same. However they are less terrible than Dire Avengers and get at least reasonably costed heavy weapons. The combat guardians are still bad.
Jetbikes are good. Cheaper and same as before from what I can tell.
Rangers seem awfully expensive for t3 models with sniper rifles, and cost even more when path finders. Did GW not learn from over pricing Waywatchers? Clearly not.
Wave Serpent is kind of a battle tank and not a transport now. Ive seen suggestions it should be using its shield to attack, but then it will open itself up to dying a lot more. Seems very pricey but I suppose it does now have the improved BS along with all the other guardians.
Elites
Wraithguard. I like. They got cheaper and now have weapon options for something which appear to be d-cannon flamers. Expect to see a lot of these, more so if the Iyanden suppliment is any good.
Wraithknights. "Combat" troops with 1 attack base. For more than chaos terminators. I think not.
Scorpions. I kind of think these got better. Mandiblasters got turned into hammer of wrath that works every round, where as the Scorpions claw is decent expecially with the strength boosting exarch power.
Banshees. Still too low strength to reliably kill power armour. Not as good as scorpions at all. Banshee masks now worse.
Harliquins. A bit odd. Veil of tears is back as it was in the old codex, but you need to cast it. Still expensive. Will die in droves should you fail to cast the spell or the enemy gets to shoot them. Not as good as scorpions.
Fire Dragons. Huge price increase. Improved saves. Still good value in all honesty.
Fast Attack.
Wow, finally got to a slot where there is competition for slots!
Swooping Hawks. Became better, and cheaper. Still have haywire grenades, fly and their guns are slightly better.
Warpspiders. I think they also became better. Against tanks their guns are better. The only real downside is most units can now "jump" away with the shoot/run option so their own gimmick is not so good.
Shining spears. Became considerably cheaper. I think otherwise they are the same. A very decent unit now.
Vyper. I think they are too expensive for how fragile they are. They can however use the laser lock rule, but since their other weapon isn't very good, I don't see many of these being used, especially given the other fast attack options are good.
New aircraft. I know one isn't in fast attack slot, but I am including them here for completion. Both are the lowest armour in the game going and will die. Too expensive by half. The Crimson hunter Exarch has perhaps something going for him, but hes really quite expensive. The Wraithfighter thing, I really just dislike. Terrify power is nothing special.
Heavy Support.
Dark Reapers. I quite like them. They are slow and purposeful and can have krak missiles. In some absurd fashion they are unable to take skyfire missiles, unlike marine and chaos marine devastators. Reaper exarch will need a mortgage to buy his gear and skills as per the last edition.
Warwalkers. I like. Powerfield makes them a bit tougher, and they can get some mileage from the laser lock.
Falcon. Probably the worst battle tank now. Out classed by the Wave serpent that doesn't take up a slot.
Fire Prism. Its pretty good, but pricey for a one gun tank. Due to deaths from glancing, rather than penetrating hits, the prism cannon will likely survive with its gun in tact. A solid choice.
Wraithlord. Still good. Can now take two heavy weapons without having to twin link them. Honestly I think this is better than the Wraithknight.
Wraithknight. Stupidly expensive jumpjet monster. Has high toughness, the same as Wraithlords, but will need to sacrifice one of its two big guns for a shield for a much needed if quite poor invulnerable save. Oddly you can't choose a mix of weapons, you have three combinations and that is all you can pick from. Can take two identical shoulder heavy weapons. Wants to take scatter lasers, so you can use laser lock on the main gun you have left with the shield.
Night spinner. Became worse I think. I don't really like it. Just take a fire prism.
Support platforms. Still good. D-cannon is expensive, but possibly very scary. All D-weapons are very decent.