hmmmm... it's an interesting idea, but a few problems i see;
as a general 'take on anyone' army, you're only really threatening units are the tactical squad's rocket launchers...
however, as an anti-'nid army, i think you'll find the list won't be quite as effective as it may appear on paper;
- overall your effective 'engagement range' is only 24", while the bugs can easily circumvent your rapid fire range...
- you have very little that can actively take down long-ranged synapse bugs like zoanthropes, while warriors w/extended carapace bio-morph will prove a challenge due to a lack of ap4 guns and two wounds apiece.
- the higher I rending attacks will still hurt!
basically, the bugs can safely mass their forces at arms length while feeding you sacrifical units like hormagaunts and 'stealers to tie-up your firing lanes and/or bog your units down into a massive slugfest!
also, what happens if say as your opponent, i were to pull out a pair of 'quick draw' tyrants w/2x twin-linked devourers?! maybe even add in some 'fexes just to be evil... you will have difficulty trying to cause enough saves with bolters to get through a 2+ extended carapace save of the big gribblies, and if they do hit your lines, they'll have *alot* of fun due to your lack of power fists...
overall, i honestly think it could be a very close game as 100+ marines is a real challenge! but imho alot will depend on things like terrain placement and the ratio of the various terrain sizes...
if the bugs are smart, they can use the cover to create blind spots - blocking your firing lanes with a combat or two while they overwhelm a single portion of your lines... (at least, that's how i'd go about it
)
what i might consider is droping 1 devastator squad to give the assault squads flamers and kit the other 2 devi squads out with 4 heavy bolters each. cliche i know, but against 'nids, high volumes of ap4 firepower is so very important as it really helps clear out warriors and 'stealers!
hope this helps,
cheers!