There get (origanal or what!!). I play em because I got fed up of fielding space marines that are basically elite... With orks, You can lose masses of Orks and still have a very effective army ( I play Goffs...lots of basic orks). They are pretty easy and quick to paint as well and you dont have to paint each one up to a high standard, there orks, they look rough anyway.
Basic orks are some of the best infranty in the game for damage potenial (with the expection of Str 3). Slugga boyz get 4 attacks on the charge, all for 9 points a peice, and field em in large groups and morle checks dont play a part for the first half of the game (unless you go wondering up the middle into a fire base!!
Ork Nobz are great and with the new assault rules, have become even better (Most of my guys are getting new shiny power claws) and are again pretty cheap and with 2 wounds are better than most expensive 1 wound guys.
Choppa, these are great. Reducing all saves to 4+ can really worry people and force them into mistakes and makes SM Terminatros damn right unless against normal boyz. My Warboss only armed with a Choppa and Big Shotta, in two rounds of combat went through five Chaos Terminators without a being touched (about 90 pts).
Ork Trucks are get transports, respecially for Trukk Boyz as they only get had on a 6! Burn it into your enemies fire base and which the confusion!!!
Well, there you go, hope this helps
PS You can also take a Baslisk, annoy's marine players no end ( trust me!!