You seriously lack anti-tank. If you're thinking of an anit-nid list, you'll also need something to kill monstrous creatures.
Devastator squads should have a model with a bolter for every model with a heavy weapon. I would move a few marines from each tac squad to the devastator squads. Infiltrate, while nice, may not be a huge help with this list, since the rest of the army is slow, so if you don't deploy the devs at least near to your deployment zone, you'll leave the devastators unsupported. Consider putting two missile launcher squads in the elite slots, and giving them tank hunter instead for some anti-tank punch.
The 7 man tac squad doesn't seem to have much purpose. You need at least one squad equipped for close combat, preferably assault marines if you can find the points. Give the captain a power weapon to help out if the enemy breaks through your lines. Also consider bumping him up to a master. The extra point of leadership is really worthwhile with this many marines.
I'd drop a model or two from the landspeeder squadrons and equip some assault cannons instead. Smaller squadrons are easier to work with, and the assault cannons will help your anti-tank, while still being a good anti-hoard weapon.