Food For Thought - Good Fliers and Bad Fliers on 3++
Abuse Puppy raises some very good points in this article covering fliers over on 3++.
Other than being hard to hit, the big point for me is that fliers can potentially swing 5/6 games by dropping clearing/claiming an objective. Now this isn't exactly breaking news, but there are still a lot of lists and discussions I've seen that take the 'ignore the flier' route.
Unless your army has similar inherent mobility (e.g. scoring bikers), I feel that ignoring the fact that your opponent can pick at least one objective to land on late game is almost handing your opponent the game. For me it's that important. Sure you can focus on the ground elements, but against a balanced lists (take Josh Roberts' Caledonian winning Necron force for example), that's easier said than done.
I would note that tournament specific missions and scoring make a big difference. NOVA is the obvious example here, but I'm sure there are others where custom rules make a difference to how you build and play your army to best effect (if you choose to tailor your lists for particular events).
I'm not sure if the rumoured Death From The Skies fliers compendium will change the balance of any of the older fliers in particular, but I think the principles of a good flier - typically a points efficient transport with mid-strength or better guns (the aforementioned vendetta and night scythe) or just very killy (helldrake) will stand, even if the units themselves change in time.
Anyway, something to consider when planning how to claim and defend those objectives!