Our two boys are 3yrs apart. They have shared a bedroom for 18mths and they love it. The only thing we had to change was put them to bed at separate times as inititally we put them to bed at the same time and they thought it was party time not sleep time.
Now DS1 is old enough to understand we have explained that he shouldn't wake DS2 in the morning and let him sleep. If they wake up at the same time they play together in their bedroom. I think putting them in the same room has helped them both sleep better. They are great mates and quite often play together in their room during the day with their 'babies' and imagninations.
I also find that once they are alseep they don't wake each other up with their noises..they are both heavy sleepers.