Well, Dark Eldar are on the horizon, and to say that I am excited would be a massive understatement.
I have been playing Dark Eldar for about as year and a half now, as a break from my Jetbike Eldar list. I must say that even for an old book, the army is really fun. Dark Eldar was the army that got me into Warhammer 40k, along with the Witch Hunters, so seeing them get a new book is awesome. Way back in the day I only played Fantasy, and I considered 40k to be a "lesser game." That all changed when I read an article in a White Dwarf where someone described the in-depth tactics and strategies on how to play Dark Eldar. I saw much more complexity in this game than I ever knew existed, and I was hooked.
I waited, and I waited for a new book with better models, because I just couldn't shell out the cash for those old hideous units. Last spring I got tired of waiting, so I started converting and working on my own models.
With the advent of a new Dark Eldary era upon us my efforts for converting have waned, because the new models are just spectacular.
All in all my raider-heavy list built for speed hasn't changed much at all except for the strength through pain special rule that will make my wyches and incubi much more resilient. The reworked units (pretty much everything else in the army) seem like they are in general much better and more viable and the new stuff looks cool too so hopefully there will be all sorts of different armies cropping up.
That isn't to say that everything is great, the book is an improvement to be sure, but there are some changes that I really question.
First off dark eldar jetbikes, no longer give +1 strength or a 4+ save, and HQs no longer get the option to be mounted on them. This one is a biggy, there is a HUGE drop in their battle effectiveness for the ability to turbo-boost 36" and do a weak flyby attack. I would expect a larger points drop for what they lost...pretty much the ability to kill things and not die when sneezed on. Turbo boosting that far is cool and all, but a 3+ cover can only get you so far, and I really don't see this unit being able to kill anything in close combat or shooting without dieing instantly.
The splinter rifle is still rapid fire, and warriors are still mediocre. Enough said here really, not a huge problem, as the army has plenty other ways to deal damage, but it would have been nice to give the basic warrior the option to be a light assault unit for fun. I will try new weapon loadouts on my warriors to see if I can get them to be more effective. Overall warriors continue to be pretty sub-par as a core unit compared to everything else in the game.
Hellions can pull independent characters out of units when they hit an run. This rule is pure fun, but I just don't see it being something that I would want to do every game. Since it is used as part of a hit-and-run move it just isn't that tactically sound. All I can see it being used for is to separate characters from a unit that gives them buffs or vice versa (like pulling a Weirdboy to lower his leadership from mob rule so he can't pass psychic tests).
Incubi squads can't have warriors in them anymore. Right now, I wound allocate on my Archon bodyguard like crazy, it really makes them the only unit in the book who can take a beating. Armor ignoring wounds can go to the warriors who have crap armor anyway, keeping those Incubi alive and kicking. Feel no Pain won't help this much, so it seems like Incubi will be less resilient in the new book for against people who really want them dead (which is everybody).'
Those are the big ones that rub me the wrong way, but overall I must say that new is good for the Dark Eldar.