Theyre very interesting. Very nasty weaponry but not in large quanitites per ship (or range). Theyre very fast and agile and you can field a nice swarm of them. Individually their ships are quite fragile and rather vulnerable to big beam hits though I must say the Gravitic Energy Grids (even the 1 point of it on the smaller ships) is ALOT more effective than Id givent them credit for. The best description I can think of in play style is sort of a cross between ISA and Drazi. Lots of swarmy ships but they feel sort of whitestarish, being able to take more damage than you think they might and few, but nasty weapons.
I played a couple of test games in Vassal (I added them into the mod) against myself (yes I'm sad but I get bored sometimes

) both at 5 point raid with the following drakh fleet:
1 Carrier (carrying 4 Light Raiders against the ISA and 4 Heavy Raiders against the EA)
4 Raiders
3 Scouts
The first game was against 5 Whitestars and was brutal, ending up with all the Whitestars destroyed, and only 2 Drakh scouts and 4 flights of Nials left on the table. It was a reasonable win for the ISA on victory points.
The second was against 3 Chronos and 1 Apollo and was again fairly brutal but without their intercepors for the most part the drakh weaponry was simply too much for the EA who were wiped out for the loss of 3 heavy raiders (though the rest of the drakh fleet had take quite a bit of damage and one ship had lost its weapons permanently).
All in all the Drakh seem to be rather fun to play (and well balanced too) though I'm not sure how well theyll fair against a 'big beam' fleet like Minbari, Centauri or the First Ones. (Though they should do ok against Vorlons as they have a HUGE manuever advantage in this case)