Outstanding player, but there were two issues for me why it didn't work out:
1. You ended up with a post-peak Veron. Physically the level he produced at Sampdoria, Parma and Lazio was a lot higher than what he showed at United, Chelsea and Inter. He spoke about how he didn't get a proper pre-season when joining United and went into the season under-cooked. Peak Veron wasn't a light-weight playmaker, rather an all-round midfielder who could compete with the likes of Edgar Davids for club and country. He recovered his groove at Inter and Estudiantes, but he was a slightly different player by that point for me.
2. I don't think he was totally compatible with Keane, who by that stage in his career was clearly the main man kick-starting moves in midfield. There are games that Veron played with Phil Neville which he dominated, despite playing with a 'weaker' partner. United didn't really need Veron in the league when Keane already provided that central control. Of course he did shine in the Champions League, where Ferguson wanted a more patient probing approach, rather than the helter skelter that contributed to their defeat to Real the previous year.