This is the first part of probably about three where in an attempt to get some content on the blog I am going to talk about what I've learnt.
First of all you have the chance to take a defence line, making all of your units more durable. You have probably the most advantageous piece of terrain in your deployment zone - so why bother moving?
Then there's the fact that your opponent, unless they are an equally shoots army, has to move across the board to get to you, getting blasted to smithereens by your long range firepower along the way. If used to good effect, a "shooty" army may basically have 2-3 more turns of action than an assault one. Quite compelling evidence that shooting is king in 6th.
Moving onto the opponent reaching your lines, irregardless of how they manage, your firepower should still be enough to blast them away, especially since they've probably been forced out into the open, while you're just there enjoying the 4+ cover save.
Say the enemy decides to charge you. What benefits do assault units get? None... What do you get? A bucket load of over watch shots even if they don't decide to multi-charge and you also get to strike first at initiative 10 while the opposition is busy clambering over your defence line.
Add in a bit of mobility for some last second objective grabbing or just some nasty deep-strike/outflank surprises to disrupt the enemy's backfield and you've got a pretty lethal combination. Through some cheeky deployment even flyers will struggle to really hurt something like this.
So having said all this, you guys must be thinking, "Hang on then, if this is so amazing, Dimitry, why don't you do exactly this?"
Well there are several problems. First of all, this is a VERY boring style of list to play, especially if you've gone for the more static approach. It also takes ages to finish matches if you plan on moving anywhere past your deploy,net zone. On top of this, such lists often are associated with huge numbers of models... Not everyone can afford the time and dedication to make something like this, let alone the money. And finally, some armies can and will probably destroy you anyway no matter how hard you try.
Slightly off topic but, one of the main things I've found so far, is that it's now increasingly difficult to make a balanced all comers list. With all the armies, play styles and the addition of imperial armour, there's just too much too account for, so perhaps you need to now simplify stuff and just say this is my dedicated anti-tank, and this my anti-infantry. Good, multi-purpose units are so important now - obliterators - I'm looking at you.