If your having trouble with speed freaks make sure you have autocannons in your infantry squads. There perfect for wasting av:10.
I would also make sure you have some counter assualt, ogryn are very effective against regular boyz squads.
I would also stay in cover (duh!) and take advantage of close order drill. Youll get initiative 4, so at the worst you srtike at the same time.
orks are slow, so one or two flamers might be useful. Definetly space out like soporific said, deny massacre moves into your squads then rapid fire away. Lasguns are useful against orks, especially when your rapid firing 60 shots into them.
Also, be wary of which trukk has his boss in it. lots of times these CS's are tooled up in mega armour which can be a real bitch.
The time to strike against speed freaks is when they just moved. orks are slow so most ork players will get as close as possible with their 24in trukk movement, often leaving them in the open. Hit the transports with autocannons, then use your templates to smack them around. Thin them out ebough so that you can finish them off with the bayonet.
Also, dont be afround to counter assualt boyz, there t4, but have a 6+ save. 25 bayonet attacks can be effective.
also, remeber that your officers are there for ld purposes, not to assualt a mob of 20 boyz. They are not space marine comanders. Youll need them to keep your army on the board. This is not to say they can assist in assualt, but just make sure there in a winnable fight.
Hope this helps