Basically they sold their organically grown PBM used the money to by DSCM and pocketed a cool $100 million in the process.
They paid $140 for every DSCM customer. I would venture a guess that it takes much more than that in acquisition costs for new customers. (acquisition would include marketing costs such as print, radio, tv, etc.) This will give them the opportunity to bring all of these customers over to their website. Also bringing brand loyalty in to the fold.
Integration will not be difficult here. It is an online provider and mail order fullfilment and the intergration here will be fairly simple, no other way to see it.