(I'm trying to have discussions here, but it's not that easy when nobody responds...)
I tried out Hunters and Stalkers for the first time yesterday! It was a game against a CSM player - I had an Iron Hands Rhino Rush with a Command Squad on Bikes, the Hunter/Stalker formation, and Chapter Master Smashfather. He had a Death Guard Rhino Rush with a bike squad, the three-Helldrake formation, and a lord on a bike. Mirror match! (I also had a Librarius Conclave and he had Havocs, but that's not a mirror match.
Anyways, it was a close game - I may post a battle report later, because it was pretty cool how it went. I'm not going to regale you with tales here, though, because that's not what this post is for!
This post is for my thoughts on the anti-air.
And overall? Stalkers are pretty great, Hunters are... Less so.
I had something like 320 points of anti-air, three Stalkers and one Hunter, and he brought 510 points of pure Helldrake. Thanks to the insane volume of fire that my Hunters could put out with Interceptor shots, (9 ignores-cover shots per target,) I was able to incapacitate a Helldrake on turn two (I got a hull point on each, and a Weapon Destroyed result on one,) I put two Hull Points on his third Helldrake when it came in turn three, and finished off the weakened one with the working gun when it came in from ongoing reserves on turn four. Ignoring Cover (the bonus for having three) wasn't as big of a deal as it might have been, since he had that 5+ invuln, but it did get me a Hull Point that I wouldn't have gotten otherwise, and being able to fire at multiple targets with a single unit was invaluable for dealing with target saturation, and when there was only a single target, being able to buff up their damage was similarly invaluable. Having these guys didn't just kill fliers for me, it was able to neutralize potential sources of damage before those sources got to hurt me, so they boosted both my offensive AND defensive capabilities.
Unfortunately, in order to bring those Stalkers are part of a Medusa Strike Force, I had to bring in an Anti-Air Defense Force, which meant bringing a Hunter as well.
The Hunter DID actually get me a kill, which was neat. (On the bottom of turn four, I hit the other Helldrake that had a working gun, got past his invuln, and took out his last Hull Point.) It was the only time it got me anywhere, though - Even with Armorbane, a single BS4 shot that doesn't ignore cover is just too unreliable to cause significant damage, and the formation bonus (+1 BS for the Stalkers if they fire at something that the Hunter hit,) is completely useless - Against any decently sized air force, the Stalkers are going to be firing Interceptor every turn, or at least the first couple of turns, which are the most important ones. The Hunter cannot fire Interceptor, so it's not going to be firing with the Stalkers. This effectively nullifies any formation bonus until you get to turn 4 or 5, by which point most fliers *should* be dead.
So, the Stalkers I'm very impressed with, at least if you know you're going to be facing fliers, or at least skimmers. Bringing three for 240 points (You ARE buying Storm Bolters for all of them to soak up Weapon Destroyed results, right?) provides enough AA for just about any potential threat. The Hunters... Well, their model looks nice, and they're not the worst tax you could pay, right?
(If you expect to face FMCs and not Fliers, by the way, the Hunters are a little better - Punching through armor saves is nice, and they actually get to use their formation bonus. Plus, if you take them in a Medusa Strike Force like I did, you can bring two, use PotMS to fire them at two different targets, and then have the Stalkers fire with BS5 at both targets. It's just not good against actual Fliers, which is ironic considering it has Armorbane.)