I live quite close by, albeit a little closer to Drumcondra than Ballybough. I do like the area, when I moved in I had some trepidation but for the most part things have been fine.
The negatives for anyone looking to move in there are its proximity to Croke Park. Where I am this isn't so much an issue, I am the far side of the road and my house is set back nicely, but for the houses on St. James' the opposite is true. The front doors are on the paths, and the paths will be chaotically busy on big match days. Parking is unreserved, it's a free for all, which is both good and bad.
Sadly, some of the roads off Clonliffe Road have a down-at-heel vibe to them, and I don't particularly like the little alleyways that run in between and behind houses, from both aesthetic and security perspectives. You do see some illegal dumping in these streets. Generally the area starts to lose its charm from James' on down to Foster Terrace and Clonliffe ave. etc.
There is also the fact the train line bisects the street, which means the noise and inconvenience from early 'til late (its severity will depend on the exact location of the house).
I don't imagine you'd have trouble getting tenants, but factor in the above in your expectations of a rental yield. It is not as desirable as Clonliffe Road or Drumcondra proper.