I shoot a bow in RL. Wooden recurved bow actually.
Of course arrow has the most speed just after it has been shot, but the speed doesnt lower too dramatically after that either. You probably wouldnt notice a big difference of and arrow shot from 10 meter or 100 meters.
I think bows are pretty realistic in M&B, although they are a bit underpowered. In mediavel times bows were HEAVY. There have been found old longbows up to 200lb and I could say noone could pull a bow like that these days. 50lb is pretty typical hunting bow weight and you could even penetrate a moose with it, unless you hit any big bones. And not everyone would have the strength to pull 50lb bow either.
Bows should be actually more powerfull than most crossbows. Even though crossbow would be heavyer to pull than a bow it could still be less powerfull. Bows have longer arrows since have longer pull. This means that the string pushes the arrow forward for a longer way and this gives the arrow more velocity.
IMO the shooting system in M&B is pretty nice. Actually its the best i have seen. But there are some things that seems pretty funny. In RL archer should allways be able to keep their bow in full draw for attleast 10 seconds without any shaking. In M&B you cant hit anything if you pull the bow more than like 3 seconds. You really cant get tired that soon.

Attleast if you have powerdraw hight over the bows powerdraw requirements.
And if you shoot a naked river pirate with a war bow, the arrow really doesnt get stuck in the guys chest. It would go all the way through and it could kill several other river pirates standing behind the first one.

I know people who have shot 2 deers with 1 arrow.