Alright, the Dark Eldar are here now, my period of absence is over. Later I'll put something up regarding mechanics and possible hints at the future, but right now, the Hornet. The rules can be found here.
In my opinion, it's much harder to design new vehicles (except Walkers) than units, mainly because you have less options available to you. There are less possible configurations, stats and options. For example, the Raider and the Trukk are really rather similar except one floats and one misses with most of its shots.
The Hornet falls into the 'mobile heavy weapon vehicle' category in the Eldar Codex, a space it shares with the Vyper and the War Walker, and it almost immediately eclipses the Vyper. For 65 points I can get a Vyper with star engines and a shuriken cannon. For the same cost I can have a Hornet, which has two shuriken cannons, star engines for free and two better armour. On top of this, the Hornet isn't open-topped, and can Scout.
The War Walker also Scouts and is cheaper, but its also slower. Plus, it's a Heavy choice, which means its competing with the Falcon and the Wraithlord, and to a lesser extent Prisms and Reapers. The Hornet on the other hand competes with... not much at a competitive level. It seems like a no-brainer to take it over its competitors then.
The shiny new bit of the Hornet is that it can take Pulse Lasers, usually the sole domain of the Falcon. However this is expensive and hence I'd go for a pair of Bright Lances, Scatter Lasers or the EML.
Overall then, the Hornet seems a brilliant Fast Attack choice, at the expense of making two other units completely redundant. This may be a fault of the actual Codex rather than anything else (many units seem too expensive for what they do compared to other armies), in which case consider this an excellent fix.