Should be a decent list against marines. Lots of AP 3 there. Probably fun to play too. Not all that tactically sound though.
For instance, your only unit that can capture objectives is a single 20-man grot mob (vehicles can't capture objectives no matter what FOC slot they are so the dreads don't count). Also, your battlewagons can fire no other shots if they fire their killkannons because they're ordnance, making those zzap guns and big shootas pretty useless til you get a weapon destroyed result.
Tyranids would make quick work of this list though. Fexes with venom cannons will make quick work of your tanks because they're open-topped as well as your dreads, you have no way to deal with MCs effectively (all your high str weapons are ap 3 vs. tyranid MCs typical 2+ save except your 3 bs 2 zzap guns which may or may not have a decent str and a CC hive tyrant will tear through your dreads like paper since it strikes before they do and rolls 2d6+str for pen and has more attacks). An ork horde list would similarly tear right on through with powerklaws hidden in mobs. Anyone else would be a tossup depending on what they were fielding, mostly in the other army's favor if they've got a decent list though.
Suggestions for improvement: Combine the 3 tankbusta squads into 2 and put the big mek with shokk attack gun in a battlewagon and give it a 'ard case. Then that wagon is pretty much for fire support but will do it fairly well. It's not really an optimal unit at around 300 points for 2 blast templates, but it's better than leaving the mek alone. I'd toss him out entirely and get either another KFF or drop the 3rd battlewagon for a unit of Kans with grotzookas for hilarious awesome anti-infantry that's also tougher and more killy in CC than a dread for the same points. If you want to keep the 3rd battlewagon (which is a good idea), get some nobs and give it to them as a transport. Or you could get a warboss, take the nobs as a troops choice, then put them all in the battlewagon. Mega-armor warboss + meganobz in a transport is a pretty solid option. 'Eavy armor Nobz and a 'eavy armor warboss in a battlewagon works well too.