Hey Wydrr. Yes, though much maligned Dark Eldar can still bring the pain. Lawrence from Tabletop Tactics is a dedicated Dark Eldar player and has won the No Retreat GT (from SN Battlereports) three times in row with pure Dark Eldar. The DE community is extremely pessimistic and cynical, but in reality the army is still good and can compete.
Their best units are Kabalite Warriors, Venoms, Reaver Jetbikes, Razorwing Jetfighters and the deadly Talos pain-engine (in particular using the Corpse Thief Claw formation from the Haemonuculus Covens book). But simply put Kabalite Warriors in Venoms supported by multiple groups of Reavers is extremely deadly and can catch people totally unawares.
The Reavers have great jink saves and shred people in close-combat with their incredible hammer of wrath attacks with their cluster caltrop upgrades. They are ultra-fast (fastest unit in the game) and can also bring great shooting via the Blasters which can bust tanks.
The Kabalites in Venoms just bring incredible amounts of shooting, extreme mobility and are great scoring options (Reavers too) in maelstrom type games.
They have a variety of units are good support units like Mandrakes (despite their reputation), Scourge and even small units of Incubi are very effective at mulching Marines and holding the line.
If you want to see Lawrence's list and see the results of his games checkVox Cast Transmission 13: No Retreat III Tournament Report - YouTube
His previous lists were all fairly different... whether it be pain engines, flyers or MSU Reavers.
Also check out the Splintermind Podcast (which I've participated in the past) where they talk to Skari and Lawrence about what works for DE. Its probably the best DE primer you could ask for. Its episode 26- Skari and the Spider.
I definitley plan on getting back to my DE soon. I really want to give the Reavers a whirl since they are amongst my favorite models in the DE line. Anyway Wydrr hope that gives you a decent overview... Splintermind: The Dark Eldar Podcast
If you have any more questions I'm happy to help