So, there are two options here: the Executioner and Infernous. We'll take a peek at the Executioner first as we are more likely to see it come into being with Dark Angels.
It's basically a Leman Russ Executioner but in Space Marine form with the added advantages and disadvantages. Its base price is already that of an upgraded Predator meaning this vehicle isn't going to be cheap but it comes a heavy 3 plasma cannon. Not bad, particularly in 6th edition where cover is less and far less prevalent unit wide and where big gun tanks are a lot less vulnerable to being suppressed or having their main gun shot off. Oh and no Gets Hot! which is nice.
The Executioner has the usual upgrades and sponsons allowed as well. Heavy Bolters at 20 points are a decent buy - they give some reliable firepower outside of the blasts and with the new way wound allocation works, the plasma wounds won't be wasted like before. Lascannons at 60 points are way too steep though - that brings the price close to 200 points and although it becomes more reliable against vehicles, there are way more efficient choices out there. The Plasma Destroyer may also be replaced with a Heavy Conversion Beamer (aka Conversion Beamer with a 5" blast) which is only really nice at 42"+ - not something which you can always rely upon getting.
All in all it's not a bad option for busting low AP models in 6th edition though a bit pricier than your average Predator (145 with HBolters).
The other new Predator from Forgeworld is the Infernous. Not hard to guess what it does. Five points more expensive than your basic Predator, this replaces the autocannon with a Flamestorm cannon. This sucks unless your Blood Angels with the Fast rule and hey...don't you have that option already? Shockingly Blood Angels can't take this option but the other Marine variants can but it's still not something you're looking for.
However, the main weapon can be upgraded to a super duper Melta cannon. Think Devildog but with a 5" blast. With the new blast rules this is pretty good as you have a longer ranged melta weapon than normally (though not as long as an MM) and even if you nick opposing tanks, you're going to be landing S8 AP1 hits at the minimum. It's an expensive upgrade though at 30 points and along with potential sponsons, again makes the Predator a bit more expensive than usual at 140 points with HBolters (again, the best choice). However, range 18", side AV11 and combat changes to tanks makes this option a lot more vulnerable to being, well smashed in the face. Glancing AV11 three times is a lot easier than AV13. 18" range puts you in enemy melta range so AV13 is less of a deal to cope with. 18" also puts you within combat range of even the slowest enemy Troops and that surely spells Doom for most vehicles sooner rather than later. And that's before you get to melta-range at 9".
Conclusion
All in all, not bad in terms of the top guns (Plasma Destroyer & Magna-Melta Cannon) options. They are both blasts which are better in 6th and low AP, also better in 6th though the Predators are still more expensive than what one is used to paying, even for the ACLC Preds in Blood Angels. And these variants certainly don't have fast but they aren't breaking the bank significantly either - both clocking in less than 150 points. Standard Predator chassis is nice as well with front AV13 but the Infernous variant isn't going to be able to maximise this as much as the Executioner due to the shorter range on its main weapon which opens it up to side shots at AV11 - much, much weaker. This, in general, makes the Infernous variant a lot less viable as a solid option compared to the Executioner.
