Some Pros
Your bunny will enjoy having the company of another rabbit
If they play together, that is better entertainment than any tv show
As long as both are healthy, I suspect that bonding two rabbits improves chances of them living longer (just my theory, mind you)
Twice the love for your bunny; twice the love for you
Some Cons
Twice the vet bills (a big consideration)
Twice the food bills
Twice the cage space (if they are housed in cages for any length of time)
Spay/neuter must be considered if bonding
Bonding may not work
If your present rabbit is close to you, that might change somewhat as the rabbit bonds with the new bunny...you could feel like you are being neglected