At first I wasn't too excited about the prospects of McDavid staying with a guy like Hall, but the more I thought about, the more I realized how good of a idea it is.
Considering McDavid's value to this team, it's extremely unlikely that the OEG is going to let him live on his accord with Hallsy. Chances are there's going to be an extensive amount of baby sitting and watchful eyes around McDavid and indirectly Hall. McDavid's constant monitoring can be a great opportunity for Hall to maintain his focus from the last half of the 14-15 season, and prevent him from going astray. Not to mention the pressure Hall would be under to make sure McDavid isn't screwing around under his influence.
This also allows McDavid and Hall to gain a fair amount of chemistry off-ice, which helps chemistry on-ice no doubt.
Ference or Smyth would've been great billet's but McDavid is already such a mature and focused young player, he deserves to be with players closer to his own age. I believe Hall has matured a fair amount since even a year ago, and I think Connor and Taylor will be productive roommates.