I have 8 year old fraternal twin boys. I think the first year was the hardest, especially since one had terrible reflux issues. Once that was resolved at about 14 months, it's really been easier I think than my friends with singletons.
My boys seem to be best friends outside of school. They are in the same class at school, but you'd never really know they were even brothers in school. They have their own interests.
That said, we've never had a problem with shared gifts (things that can really be shared, like games, playdoh, etc).
I didn't dress them alike as infants and toddlers, but when they hit about 4 they wanted to have the same shirt, shoes, etc. Now they choose their clothes for the day and sometimes still end up with the same shirt; however, one prefers denim shorts and the other khaki.
They also prefer to share a room. We have another room if one of them didn't want the one they share. One night one of them wanted to sleep in the other room and did. Never asked about it again.
They also take turns staying the night with grandma. Gives them some one-to-one time (for both). When they get invited to others' homes (and they always get invited together), most times they both go, but sometimes only 1.
Our neighbors until recently were twins girls 5 months younger than our boys. My SIL has a twin brother. I think b/g twins relationships play out a quite different.
(and family in both Southern CA and Florida) because they've been to WDW 3 times, and DL twice! But no more trips planned until next fall. I am going to hate paying for their tickets 
but I do remember that we attracted a lot of attention when we were out and about with them during their infant months. Now we just attract attention in public because we have a lot of kids 
