One of the things that has been bothering me as of late is the number of reviews, especially before the book was released, that were extremely wrong. I understand that some players use many armies, and most don't specialise in playing Aeldari, but without consulting someone who does specialise in this force as their main army means there are a lot of items mentioned in previews are wrong or not possible. As someone who specialises in this force I'll give my quick take and hopefully make some corrections. As a note, I tend more towards narrative play than match play and my army is locked in to Ulthwe, so you won't see the "everything is -x to hit" expectations coming from me.
Overall Grade: B+
Things You Need to Know
Phoenix Lords cannot take Warlord Traits... not any. Most people are aware that Phoenix Lords have a special rule that allows them to not make you lose your <Craftworld> bonus, but many people did not realise there is another rule above the specific Craftworld traits that prohibits Phoenix Lords from ever getting a Warlord Trait.
Normal Crimson Hunters are BS 2+ in their top damage tier. This is actually no different from Index 1 and was done by design so they could still hit on a 3+ when moving. I am still amazed how many times I've seen people argue that only the Exarch is BS 2+, but I'd recommend people carefully read the book cover to cover, for the rules section at least, as if it's a totally new book.
Support Weapons become individual units once deployed. This is very important as I continue to see people discuss casting Guide on the unit as if they're a single unit, but that is not the case.
If the Autarch is entering through some form of the new Deep Strike you can not regenerate (path of command) or generate (Ulthwe Warlord Trait) Command Points until AFTER they have been deployed. This is important to remember because using the Webway Strike stratagem can potentially be regenerated if the model is already on the table.
Sunburst grenades were re-named back to Plasma grenades. I have no idea why, but I wouldn't mind if they made up their mind on that one.
The Good Stuff
Really, most of the book. With the exception of Wraith units nearly everything received a point reduction between 10-25%. The individual rules for units were rarely an issue, but the costs were. I give GW kudos for recognising that, aggressively correcting points, and not fudging around with the rules too much, only lightly making tweaks.
Howling Banshees: They're so cheap and so fast. I'm having a difficult time not imaging them becoming a mainstay unit for every variation of Eldar.
Runes of Battle: They really make me wish I rolled better for casting psychic powers because there isn't a power in the list that I don't like. It makes me want to play really large Apocalypse games just to get to cast all the powers.
Fire Prisms: I'm not certain my rolling will improve with them at all... but with the chance to shoot twice... It's like they know I'm ready to love them again.
The Great Stuff
The Stratagems are going to be what lets players set this army apart. Now I'm not just building a list... I'm building a list around Stratagems, so it's likely my army will actually play differently than other Eldar players.
The Bonesinger. The rules are spot on and its rules were released as a free downloadable PDF. As someone who has worked running corporate social media accounts, those posts tend to be planned and written weeks in advance, so it was a great surprise that it went out early enough that you could actually still order the model.
The Not-so Great Stuff
We need to talk about Warlocks.... they're not good. Other armies have psykers that are far too close to identical with the exception of having double the wounds and access to full strength Smite, something a Spiritseer provides for a 10 pt bump. Either they need to drop about 10 points per model, or they need Destructor amended to be D3 Mortal Wounds.
The Warlock Conclave is on the right track to getting better in that it's cheaper than an individual Warlock. This is good since getting an equal number of individual Warlocks was previously superior in every way. Now it's superior in nearly every way. Much like their individual unit cousin, this unit needs to drop about 10 points per model, or, their version of Destructor should be amended to D3/D6/D6+3 and they need to be able to deny 1 power per model in the unit. I will still use this unit for narrative forces, but you will likely never see them in matched play because they still widely miss the mark.
Autarch changes. Considering Grey Knights received a unit without a model and a "how to" for converting it, it seems wrong for Autarchs to have been stripped so bare. Personally I have 1 Autarch that I'm going to try salvage by converting, and one I used often that's going to be retired, and one that I'll use, but clearly has a banshee mask it can't use. It seems like an odd reduction in utility for the model and really has upset people. Skimping on extras from the plastic kit to begin with is part of the issue here. Another is that four of the relics can only go to Autarchs (being the only character that carries the appropriate piece of wargear to swap out), and the actual foot-based one can't even do that.
Some of my favourite models are being retired because their rules got dropped. While I'm not entirely surprised I am absolutely going to miss my Scorpion Exarch with Chainsabres. I was so proud of that model and still am.