A twin pregnancy certainly has its own risks and stresses, but it is wonderfully efficient.
Everyone gets a baby to hold. Although there are definitely times with 2 babies can seem like too many, I vividly remember coming home with twins and thinking how wonderful it was that my husband and I each had a baby to hold and sorry for singleton parents who had to take turns. This also comes in handy when grandparents come to visit or if there are 2 older siblings.
Many more than double the smiles and laughs.
On top of having the smiles and laughs of each baby alone, you also get the joy of seeing them smile and laugh at each other.
Watching them interact.
It is so much fun to watch twins interact, from sweet hugs and kisses to inside jokes and elaborate imaginary games. My heart melts when I see the small, unprompted gestures of kindness between them - a toddler running to get a pacifier for her sister when she sees that she is upset, or a 5 year old offering to share her eagerly awaited ice cream cone when her sister's dropped on the ground.
Built in playmates. For a while, I felt guilty about not being as on top of arranging play dates as other moms. Then I realized that I don't have the same need for play dates as singleton moms. My girls' life is a constant play date, so, although they enjoy playing with other friends, it is not as necessary to their happiness (or my sanity) to arrange play dates.
For the planning and expense of one birthday party, you get to celebrate 2 birthdays.
Blunting of separation anxiety. The transition to new situations (babysitters, preschool, a new school, etc.) is generally much easier since they get to do it together (except in the occasional situation when one totally freaks out and induces mass hysteria).
The twin bond. Twins seem to have a subconscious bond that goes beyond simply being siblings or friends. As infants, my twins always seemed very aware of each other, and I loved to see them snuggling up next to each other or reaching out to see where the other one was. Even recently, I came upstairs to find my very grown up, 5 year olds curled up in my bed, asleep, holding hands.
Having 2 beautiful, smiling, faces greet you every morning.