Lots of plusses about Noise Marines in the new Chaos Space Marine codex. They got cheaper, they can produce a prodigious amount of firepower and are dangerous in close combat due to their higher initiative. Their sonic weapons are also cheaper and the Icon of Excess looks on paper to be pretty awesome.
In comparison to the old codex, the Noise Marines now are strictly better. They have more options, and more builds. Squad upgrades include the sonic weapon (excellent price), close combat weapons (in exchange for the bolter, or instead of taking sonic blasters), Veterans of the Long War (great in a space marine heavy meta-game), Icon of Excess (making them feel no pain -- very cheap as well if there we're taking a large blob of Noise Marines), and one in ten marines can get a blastmaster.
The Noise Champion can get the doom siren, in addition to melta bombs, an odd gift of mutation as well as access to melee and ranged weapons from the armoury.
Let's have a look at the the sonic weapons to start with. The blasters have been changed to Salvo 2/3. But, we've got to remember one thing about "salvo" weapons: we cannot charge any model who has fired a salvo weapon. So if you're planning a charge, you need to switch to bolt pistols. That said, their ability to ignore cover and a range of 24" means they're always going to be pretty useful on the move, or stationary. The blastmaster on the other hand, is tremendous. Seriously! With a choice of modes (both of which ignore cover and cause pinning), this weapon singularly can cause tremendous headaches and has great range to boot. Alone, this weapon is the reason to go for 10 strong squads. For the Noise Champion, the doom siren is an interesting selection for an assault-orientated squad. The AP3 on the template weapon is clearly going to down space marines and discourage assaults.
Since there's so much here, let's turn now to consider a pair of comparably priced builds and a crazy 20 man shooty squad.
10 Noise Marines, 9 Sonic Blasters, 1 Blastmaster (237 points)
A ranged, blasting unit. Set them up in a building or ruin to start with. Only move them out to gain better range. Use as a bait by spreading them out and then falling back (not routing!), firing as they go, luring the enemy close to other guns and units. Take a bastion for fun?
6 Noise Marines, 2 sonic blasters, 4 close combat weapons, Veterans of the Long War, Icon of Excess, Noise Champion with doom siren, melta bombs and power sword, rhino with dirge caster and havoc launcher (245 points)
This is an assault orientated squad with a fluffy number of members. Get on board the rhino and fire the salvo weapons from the roof-top hatch, along with the havoc launcher to lay down a strong ground fire. Get out, rapid fire. Assault the enemy (don't forget the doom siren) or let them charge you (don't forget the doom siren). Use the champion to take out opposing champions and sergeants to secure rolls on the chaos rewards table (did he make daemon prince?). Use the Icon of Excess to buff the saving throws of your (smallish) squad and keep them alive. Once done, hop back on board the rhino and get away!
20 Noise Marines, 14 sonic blasters, 2 blastmasters, Icon of Excess, Noise Champion with Power Sword, Aegis Defence Line with Quad Gun (622 points)
Team up with a Slaaneshi sorcerer to (hopefully) get Symphony of Pain. Shoot. Then shoot some more. Then don't bother shooting some of the blasters, but shoot the blastmasters instead and maybe the quad gun. Then shoot a bit more. If in trouble, charge the enemy: the icon and high initiative should be enough. These guys are going to be a tough nut to crack. Probably strictly better to run as two 10 man squads (but then 2 Icons would be getting expensive), but what the heck: we can dream.
There's something for everyone here. And more significantly, Noise Marines just made the top tier!