Personally I thought this was a really well done episode but the main premise felt ridiculously light to me. Yes Bell was shot which was huge and very serious but Sherlocks "crimes" were not. A lot of the things brought up had no bearing on Bells shooting access to crime scenes etc and everyone including Bell and the department have been more than happy to take the results.
Sherlock followed leads to take them to a possible suspect, where he read the mans phone and spoke too loudly. That's it that's all he did and the talking to suspects for info is part of all police work. He didn't deliberately try and get the man fired, he never reported the man to parole. That the man was in such a precarious position was his own fault, he had a criminal record, he lied to his employer, he broke his parole conditions, he went and got a gun and intended to shoot someone. None of that is on Sherlock.
Up till now I would have said that Marcus was as much a friend to Sherlock as Gregson and I think Marcus was being a bit harsh although I understand he's not in the best place. However if he only allowed Sherlock to stay on the force to use him then that's out of character for the Marcus we've known is a decent guy so far.
I didn't mind this storyline just felt it would have made more sense with something bigger, more on a par with Watson's mistake when she killed a patient. I'm also not to keen on the trend the last few weeks to push for Sherlock to change, he has changed a lot since the series began at a believable rate, it would be too easy to turn him into something too different and not worth watching.