I like the deal for both sides, but I do think this undercounts the risk from the sox side in guaranteeing the next 6 years.
After 2 years, the angels had an (runner up) MVP on their hands. They leveraged their 4 years of control to get 2 additional manageable years.
The sox have...hopefully something good, but something volatile and maybe something that becomes a dH which would really hurt arb.
It's still worthwhile to do, but this is just a fair deal, if he's awesome it's a good deal, but we would have had him for 6 years at a similar total cost anyway.