I just caught up recently after watching the three anime seasons about five times. I simply love this manga and anime, it plays almost everything straight but does it amazingly.
I was hesitant to read the manga because people mentioned it's not as good as the anime and that the recent training arcs dragged and were boring. Now, I agree that it's less exciting without the great animation and music of the anime but it is still great. I disagree completely about the training arcs -- I loved them about as much as the actual matches.
Two things I'm wondering about is everyone talking about a second year. I feel like I want to see it happen but I'm not sure whether the author would like a retread of the past 100-something chapters. We'll have to go through the whole Miyagi tournament and then nationals -- and even if Karasuno lose soon (I don't see them losing in this match though) they would've gotten far. I would love to see the dynamic of new members and how the team handles the third-years being gone, but I'm thinking the author may not do it for fear of being stale.
The second thing is how they'll handle Kinoshita and Yamaguchi-- they both seem to be fulfilling the same role. In real life one of them will turn out better (the manga seems to indicate that Kinoshita is more talented) and the other one will just get shoved out, but maybe one of them will diversify or something.
Lastly, as someone who has been in competitive sports (well, martial arts but it's similar) I've identified with many, many things in this series.
Especially in the training arcs (unsurprisingly since the bulk of time you're training), I found it to be realistic-- it's not a stroke of genius but I haven't seen it executed this well elsewhere. For instance, going backwards to go forwards (with the reinvention of the 'freak' quick) and the slow acquiring of new skills coupled with being not as good as you can possibly be.
Particularly the recent training arc with Hinata being the ball-boy struck a chord. I was recovering from an injury recently (still am) and was forced to sit aside and just watch practices. I felt like I learnt a significant amount from just sitting down and watching normal practice (that I couldn't from just watching videos online), and I often had the feeling of "why didn't I think of that before" like Hinata (unlike him, I realised at some point that I'm looking more at people's weakpoints than I was looking at their strengths which I attempted to correct).