My mates an Ipswich fan, and they had the same deal with Keane. He came in after Ipswich finished 9th in 08/09 and was 'expected' to take them forward. However only a handful of games had been played before a lot of their fans were slating him - saying that he was destroying their team, that his signings were unknown etc etc (sound familiar). They didn't win their first game until October/November, were bottom of the table, and had scored 6 goals in 8 home games. They finished the season well ending up in 15th, and look a completely different team this season.
Change takes time - Sousa may turn out to be a flop, but I might remind you that MO'N didn't exactly have a flying start. With Pearson, he could only really take the team higher, and he did well - but from what I saw last season (limited due to where I live now) I felt we overachieved a little. The momentum we built up from our league one campaign carried us higher than a lot of people thought it would, but with the shake up over the summer that momentum is gone, and it will take time to rebuild. We just need to be patient.