A look into two of the units in the new Eldar Codex, the Warwalker and the Crimson Hunter. These are two very popular units right now, and there are is a lot of discussion on whether these units are worth putting into your lists.
Warwalkers are gun platforms on steriods. With dual Scatter Lasers, each of these lightly armoured walkers is putting out 8 shots at ballistic skill 4. So a squadron of 3 is putting out 24 S6 shots downfield, or even as they are outflanking in from reserves.
Other gun options to consider are scatter laser and bright lance, so that you can twin link your bright lance. Or just dual bright lances to really hunt down those tanks on the field. Of course the starcannon is not a bad option either sitting paired up with itself or even a scatter laser. Find the role that you need for this vehicle and go for it, it will excel at it.
Where the Warwalker gets expensive, is when you decide to try flakk missiles on them. Point wise, reapers are a better choice when it comes to anti-air, as your single walker hits 100pts with just the missiles on them. With the limitations of anti-air eldar have, this is the biggest qualm I have with Warwalkers, as the heavy support choices of eldar are some of the best means to deal with air.
Making the Warwalker strong of course is the battle focus and fleet. This gives you the ability to fire your guns and duck out into cover. Of course you already get a 5+ from your powerfield, or if you go nuts with holofields on these, a 4+ cover is nothing to sneeze about once in cover.
The Crimson Hunter is an expensive flyer with practically no armour. Sitting at armour 10, small arms fire (bolters) will take this expensive flyer out of the air. What it excels at though, is taking on other flyers, and if your list does not have a decent amount of anti air in the heavy support roles of your list, this is the only other option you have.
Two things keep the Crimson Hunter alive and valuable on the tabletop. Going second and reserve manipulation. With that in mind, you will need an Autarch to manipulate the reserve rolls if you are stuck going first, as a Crimson Hunter caught out in the open is a dead flyer, who is especially vulnerable to interceptors. You want your opponents air on the table first, and you need other interceptors dead.
Now once you are on the table fighting, Vector Dancer alone can help you stay out of too much small arms fire. It is excellent at keeping you were you want to be.