Of course it has been disappointing to see JO hurt for so long but I really think it's all good for the long run, which means the rest of the season and the playoffs.
When you look at it, JO never had a chance to really sit down for long stretches these last 2 years in Miami because he was basically the 2nd best player on that team. In Boston, he has had the opportunity to sit down for weeks now and from all the reports I've read/heard he is looking very good, which means, in my opinion, that he played through a knee injury right from the start of the season.
Now if he is fully rested he should play at a good level when he comes back and slowly find his rythm, and then hopefully will stay injury free (although I'm not really optimistic about that).
Anyway, I'd rather see JO take his time even if we're short handed than rush back because he looks like a player who can't heal well when playing through the pain.