His age and the fact he relies heavily on pace would be a major downside, not to mention his attitude and scoring record in England all count against him.
Teams would fear seeing him on the team lineup more than Ameobi, Ranger, Best et al, however we could have said the same thing about Martins.
He does seem to be scoring a lot of goals over there though. A gamble but on the right terms (sensible fee/wages) maybe worth a punt. Would certainly bring in attributes we really lack at the moment, and as you say him and Carroll on song would be a handful for defenders.
Course he's scoring a lot more goals over there, he's playing in pissing greece