I'm biased. I've never lived in a house with just one dog so I always think it's great for the furbabies to have a playmate.
That being said, having two dogs is kind of like having 2 kids: it's FAR more than double the work. You will be amazed at what new and creative trouble two dogs can get in to together
I love watching my boys play together- it gets a little loud and yappy sometimes when Rhett wants to play and Sam doesn't, but they do love chasing each other and rolling around. We do get the occasional bouts of jealousy when one has a toy the other wants, but we always manage to get it worked out.
You will lose some flexibility with two- it's not as easy to toss them both in the car and go anywhere (at least for me because Sam weighs 17 pounds.) And not all pet friendly hotels will let you stay with 2 dogs.
You already know the other drawbacks- twice the food, twice the clean up, twice the vet care bills.
But at the end of the day when Rhett and Sam are cuddled up on the couch together, it's all totally worth it to me.