Well this section shouldn't take me too long to write since there are only two options here. The previous codex had unlocks for several things to become troops from other FOC slots. Wazdakka could make Warbikers troops, a Big Mek made a Deff Dread a troop option and a Warboss unlocked a unit of Nobz. All of these options have now vanished so there's just Boyz and Gretchin left. Whilst there are many people lamenting the loss of the unlockable troops I'm not sure it's as much of an issues as people believe. Looking at it from a 6th edition perspective it would be detrimental but with 7th edition all units count as scoring. The only time Troops matter is when they form part of a Combined Arms detachment as it gives Objective Secured. It remains to be seen how popular it will be but the Ork Horde detachment opens up 3 HQs slots and potentially gives Hammer of Wrath but doesn't give Objective Secured. That means it really doesn't matter where the units have come from.
This is something GW are obviously keen to encourage and the new wave of codices will be interesting in the different force organisation charts and formations they come with. Whilst we're on that subject I'll be reviewing Waaagh! Ghazghkull when I've had a chance to go through it. From what I've read it seems like it opens up the Ork codex dramatically but for now I'll focus on the rules in the codex itself.
The slugga/choppa boy may be effectively the same but the shoota boy is now a point more expensive. This isn't a huge issue as I think you're probably better getting them into combat as quickly as possible. People will still run them though I'd expect. I'm still not totally decided on which is better. On the one hand the extra attack could make a huge difference and hits on a 4+ against most things. The shoota shots however could soften up a target before a charge. With the ability to re-roll one of the charge range dice there's less risk of killing too many and failing a charge but the issue is still there. Ultimately it'll come down to personal preference and I've got a stack of slugga/choppa boyz from Black Reach that kind of decide it for me!
Finally, it's worth noting that you can make all units into 'ard boyz now and give them 'eavy armour. Not sure I'd bother though for the cost. They end up more expensive than fire warriors in that case and will still die pretty easily. Not totally out of the question though as it would make them a lot more resilient to bolter fire etc.
Sadly for Trukk's Red Paint Job now only works when moving Flat Out but interesting the big shoota can be swapped for a rokkit for free. It's debatable which is better but I like the idea of a cheeky S8 shot from a trukk instant killing an enemy character or destroying an enemy vehicle. Trukks were never durable enough to both upgrading more than their paintjob but when it's free, why not? Throw a rokkit in the unit inside too (which are also cheaper) and you can generate quite a number of S8 shots across your army, if inaccurate ones.
Finally, interestingly boarding planks are now 10pts more expensive but give a 2" bonus to charge range. Not worth 50% increase to the cost of a trukk but still, interesting. Not sure why you'd take a stikkbomb chukka though, not that there was a reason before.
The question is, how to run your ork boyz. Neither a 30-man blob nor a 12-man trukk unit can gain any benefit from their numbers as they did with the old mob rule so I actually think the trukk unit might just have the edge now. Blast up in your trukk turn one and then call a Waaagh! turn two to all but guarantee combat. The big squads were great when they were Fearless but I'd rather lose 9 boyz to a failed morale test for 25% casualties than I would 22 boyz! As ever it depends on your playstyle and how the rest of the army is constructed. It's harder to get trukks a save from a KFF now so the castling of the old codex isn't really effective. Still, 12 boyz in a trukk with a rokkit only costs just over a hundred points and is a mobile scoring unit (with Objective Secured in the right detachment). That's assuming you don't bother with a nob of course which makes more sense in the Ork Horde detachment where you could have 9 trukks full of Orks for around 900 pts and still give you the rest of your 1,850pts to spent on heavier stuff. Tempting.
Having said all that Open Topped still causes an S4 hit on the occupants for an explosion but also for the surrounding models. Several trukks going up in a small space could be devastating to the boyz inside and being able to flame the occupants of a trukk doesn't help. Mind you, vehicle explosions are a lot less likely now.
I think the order of the day with Troops is to keep costs to a minimum. Tempting to throw in the usual nob with a klaw but since he gives you no leadership bonus the points could perhaps be better spent elsewhere. Having said that he may benefit from the challenge changes as his excess attacks can be applied to the squad if he gets called out by a sergeant.