I haven't seen him play very much but for him to have been at United, represented the England youth teams, had two fairly successful seasons at Villa in the Championship all by the time he is 25 says that there could well be a decent player there. There has been mention of a few weaknesses highlighted by Villa fans and I'm sure there are however I'm not overly concerned as he is only 25 (although poor technique is a concern - a harder skill to improve with age). Look at Carson, terrible for us however a good few years later and he is looking superb for Derby. It can take time for improvement to come so if Johnstone is good at the moment and can go on to be very good, I'd be very happy with that.