Shooting, lots and lots of shooting
Best starter HQ is a Farseer with Doom and Guide, easy to get your head around how to use those powers.
Dire Avengers are OK, their range kind of sucks since Marines can double tap at over 30 inches now.
Guardians with Shuriken cannon on the weapons platform, you can take to hits on the weapons platform, which makes them surprisingly survivable.
Rangers- really depends on the meta in your area. These used to be used a lot in top tier lists, but now marines have units specifically to remove units like these guys. Worth having in your collection, a 5 man squad is worth playing around with, but really I wouldn't start with these guys.
Crimson Hunters and Hemlocks are both great options, It is possible to use magnets to swap the configs over. You really want 2 CH, where as a single Hemlock can work well in support roles and its a psyker, so having it through out Jinx is awesome (works on invul saves too)
Night Spinner vs Fireprism. It depends on the role, Night Spinners are anti-primaris/infantry and don't require CP spend, plus they don't need LOS.. Fireprisms should be run in multiples, their main benefit is they can be used to target a variety of things not just infantry, but they really need CP spend to make them do work. You can magnetise this kit reasonably easily.
Dark Reapers are CWE answer to pretty much everything lol, super costly though as you really should be running a screening unit to protect them. I think these are still failcast, but you can find metal ones on ebay.
Shinning Spear, standout unit, but one that has been played to death, and are not terribly difficult to shoot off the table. Pairs really well with an Autarch.
Wave serpents are a contender for best transport in the game.
Everthing else based on the current rule set (which changes in a few day lol), is just usable, not outstanding or just really situational.
A word of warning with Banshees, they sound freaking awesome, but they _need_ support to work, say a warlock using empower and a Farseer dooming their target really maxes out the damage potential. While their points for the unit are not terrible, you have to consider the points for the warlock and transport (your taking a Farseer anyway ;p ), it can be more efficient to spend the points on other units. They also rarely make it into combat as they are basically the poster bunnies for CWE and no one wants a face full of power weapons
Did I mention shooting?
I, myself, haven't seen anything about a new codex but I don't read everything posted, just look at the pretty pictures
Basically they are doing to Eldar what they did with Space marines, we are getting a supplement that gives at least CWE and DE new rules, that in theory should help against the power creep of the new Space Marine supplements...