Fast Attack:
Fast Attack consists of units that attack. And are fast. And a general benchmark of whether your army is good or not is whether you want to use models from this section of the FoC (exception for Necrons. Poor Necrons).
Deffkoptas: Deffkoptas are a mixed bag. On one hand, they've received a fair cost reduction in regards to Ork Buzzsaws, making them more viable for turn-one alphastrikes. On the other hand, the inability for them to be supported by Bikers anymore is an issue. If you wish to take them, make sure you have fast threats to follow up with.
Warkoptas: I personally like these guys, barring their models (they look so...ungainly). Packing a twin-linked Deffgun, and a secondary Big Shoota, it initially looks like a poor Ork version of the Landspeeder Typhoon (which is ok, for the Typhoon is a great support unit); barring a reduction in cost, the reduced accuracy, and strength, seem to relegate this vehicle to the scrap heap...so why take them? They're rather versatile for one thing; by swapping out the secondary Big Shoota for a Skorcha, the Kopta acquires duality of purpose beyond its previous role.
Killa Kans: One of the primary staples of the current Ork codex is the Killa Kan. Decently-armored for its cost, and possessing that mix of heavy armament and utter expendability, two units of Kans tend to work well as a complement in most Ork armies, escorting Battlewagons or serving as horde control by tossing massed templates. As it stands, not a lot has changed, barring that one must take them in units of size three to five. This really doesn't hurt the Kans for lower-point games (after all, taking single Kans is the exception rather than the rule)while it lets the Kans scale upward to higher-point games, and can make for a hellishly large Kan wall for opponents to have to deal with. The primary implication of having a 4th or a 5th Kan however, lie in being able to create an even larger line of KFF-based mobile cover than before. Smaller units are better for Rokkits due to point-efficiency issues, but there's really nothing wrong with taking large units with Grotzookas.
The Mega-Tank: And finally, we've got the experimental toy. The Grot Mega-tank. It's expensive, both pointwise and moneywise, and has a lot of randomness to it. It moves like a Grot Tank (yet has no Commander to take), has the armor of a Hellhound (and can easily exceed the cost if not careful), and is armed with 5 turrets. Two of them are twin-linked, three of them are not, the weapons of choice being anything a Killa Kan or Grot Tank could normally take. Additionally, it gets the equivalent of two 10" Hellfury Missiles. While it fails to fire on rolls of 1 (meaning you use these turns to move 3d6" a turn), it otherwise counts as having Target Locks. Considering the amount of guns it can fire in a single round, it's fairly formidable. You'll want to keep a Mek or few on hand of course, just because it's a significant investment.
In short, Orks have a bit more toys to play with, and while nothing is as cheap as the Warbuggy, there is more variety in ways to kill stuff.
