He's been great at getting very decent league finishes despite having high squad turnover and (whether with the help of a DoF or not) found good replacements. He seems a likeable guy who has generally played high energy, entertaining football and bar the odd mare hasn't been outclassed tactically.
As for what more he could have done, my concerns about him are in three areas.
He has handled a high squad turnover well but he doesn't seem to have done much to either convince his board to back him or the players to stay. He seems to have hopped about quite a lot as a coach himself as well. I appreciate that is fairly standard these day but ideally would prefer someone who was looking for a longer term project and the abolity to persuade people to back him.
His cup runs have been very poor whilst in the UK - unless we do a Leicester the cups are our only realistic chance of silverware and I badly want some shiny stuff after so long without. Perhaps it is a S'ton thing - Pochettino didn't do well either iirc.
He hasn't shown much interest in using the academy lads, on the plus side he has continued to use the players that Pochettino blooded but he has only introduced one regular, Targett, since.
Some of these concerns are equally applicable to our other candidates of course, or there are completely different ones!