I'm an Eldar player who is currently up against a 2000 point Feral Ork army.
This army has got hords of Grots to shield it's Madboyz and three massive Squiggoths. This becomes an almost impossible army to beat - most armies are either "hords of the things" (the meat waves) or are made up of many fewer, very tough unit (like Space Marines). The beat the former you'd use huge amounts of are effect stuff, to beat the latter you'd use much heavier weapons that are much more selective.
This doesn't work if you have 3 Squigs in a Feral army - if you take the heavy weapons to knock out the Squigs, then you'll never be able to destroy the huge number of Orks coming at you waves. If you take area effect stuf, it'll (mostly) just bounce off the Squigs!
It's not "a fun army"! My opponent (who's been wargaming for 12 years) has just started an Ork army. He bought all the figures (including a Basilisk), but after going through all of the Ork rules junked the Basilisk and went with Ferals!
He aranges his army with the Squigs at the front, 70 - 80 Grots in lines behind (becase they're in lines, template weapons will tend to hit some models from all three units, so it's almost impossible to do enough damage to cause a moral check). Behind this he has three units of Madboyz that just can't be shot at because of the Grots. Last but not least he has three Junktrukz at the back, each loaded up with a unit, ready to rush in where needed.
Don't believe them when they say it's not a winning choice - my mate is a pure "power player" and he's taken them by choice!