It's amazing how much harder the Dark Eldar become when they don't spam buildings. :p
I've been on the receiving end of many a Hellion rush, and it's not fun, Tau seem to get cut to pieces quite bad by them. Chaos handled it slightly better but I still get outmanouvred most times, can't help it, I'm an RTS novice at best.

I just feel the Dark Eldar are a bit more interesting to play as when you try and avoid a vehicle/Hellion rush at the start.
But yeah, has anyone had any succesful experience of using T'au against Orks? That's my big hurdle at the moment, my tactics definitely need some tweaking to deal with the big green 'uns.