I'm gonna cause some nightmares with this, but how much you like Carlo will probably depend on whether you hated Justin Holl or not.
You can basically copy and paste the scouting report from one to the other:
Big, but not physical, uses size and long stick to angle people off and clog the middle, absorbs a ton of hits, good on the PK. Complimentary player who needs the right partner to be effective.
I think he's better, but not much. Probably the biggest thing he has going for him is he's proven he can do it throughout the playoff grind.
Whether or not this is a good trade will come down to how well he meshes with either McCabe or Rielly. If it works with one of them we're laughing. If not, that's a lot to give up for a bottom pair PK specialist without much bite.