The next big question on everyone's mind is how vehicles are affected by the 6th edition rule changes. They were the obviously dominate force in 5th edition to the point where foot lists were generally simply not a viable competitive option. The problem wasn't really that vehicles were so good but rather that cheap transports were so durable over the course of the game it made the game one of metal bawkses.
6th, IMO, does a very good job of changing this in theory. Tanks are tougher against single shots as they essentially go back to the 3rd/4th glance table (1/6 destroys) but over the course of a game, are less durable as glancing hits simply take off hull points (lose hull points = death). It's therefore easier to glance a vehicle or simply torrent one to death. This effect is two-fold.
Firstly, heavier tanks, you know, actual tanks - things like Predators, Land Raiders, Russes, etc. are all harder to drop, particularly at range where their higher AV comes into play. This means you're not going to see them disappear anytime soon. Dropping Rhinos/Razorbacks/Venoms/etc through hull point depreciation is a lot easier compared to Predators and the like. Essentially the heavy gun boats are pretty good. Land Raiders and the like though, well they're better but melta can still roll up and ruin their day pretty well. They are less likely to die to early long range salvos (except from Railguns and the like) but they aren't what their point cost suggests.
Secondly, spamming firepower transports is likely to be less viable - it's just too easy to take them out now due to their lower AV. Certain transports however may still make this concept work. Mass Night Scythes for example as fliers could be right pains in the behind, same with AV13 4HP Ghost Arks (hey both Necrons!). That's not to say transports aren't bad - they are just likely to see more use as transports where their firepower is often an accessory rather than the reason they are bought. You know, like Grey Knights - they want to be on foot shooting you but their transports give them extra firepower (importantly at 36") and mobility.
What this could mean is we'll likely be seeing less six+ 70-100 point transport vehicles. We might still see lots of transport vehicles like Psybacks, Rhinos, Venoms, etc. (the cheaper stuff) but they'll be more use in a Hybrid context - get infantry to their location and then provide support rather than being the actual purpose of buying the unit.
Also, it seems vehicles can no longer contest objectives. This very clearly puts more emphasis on infantry and being able to get infantry across the board (i.e. their own mobility or...transports!). Therefore sinking 1000 points into your army which cannot contest (if this is true) is going to be...limiting.
What weapons are therefore effective? Melta is just as effective as before in single shots taking out tanks - it's a 50/50 if it punches through your armor/cover. Cover is generally less as well so there's a slight increase for meltas there but this is countered by lack of glancing hits (they could still kill on 1/6) and the decrease in infantry threat range with them (can't over-extend). Otherwise everything which is AP2 in terms of shooting is just as effective, if not a bit more with the reduction in cover saves. Everything AP3 or higher got worse in terms of single shots but since these weapons are often weight of fire oriented, they are more likely to simply drop a tank through Hull Point depreciation. We might see a little reduction in melta use - particularly infantry based but things like fast vehicles (transports included) and Bike platforms are still excellent melta platforms. Plasma and AP2 heavy weapons might see more use elsewhere otherwise weapons with greater rates of fire are more likely to be value over an AP value of 3 (i.e. missile launchers).
Vehicles are also more vulnerable in combat - don't get caught not moving. You can still protect your infantry units with moving vehicles but don't expect them to last long. Mass attack units with Rending (i.e. Harlies, TWC, Fiends, Razorwings, Raveners/Genestealers, etc.) will rip away hull points like no tomorrow and then have a nice tank wreck to hide behind. Otherwise even Marines armed with Grenades or MCs are now very scary to tanks - no longer do they need to worry about getting a lucky 6 to hit - they're going to hit, just how much damage are they going to do?
Vehicles also get more shooting options on the move which combined with their improved ability to ignore suppression (glancing hits only remove hull points), compensates for their decreased durability. This again really helps gunboat tanks more than transports as they often have more guns - there are exceptions (Falcons, Land Raiders, potentially LasPlas RBacks, etc.) but the general theme here seems to make tanks with lots of guns act more like tanks with lots of guns and transports act more like transports. We may still see a lot of tanks on the tabletop but likely in a different capacity to what they were in 5th edition and we'll very likely see more infantry getting out of their tanks on a voluntary basis.
Again, these are just preliminary thoughts so let's get some more discussion rolling!
