Was in the original beta, but didn't really start playing regularly till just after launch. The game was very different, but great nonetheless. There was a lot more AT synergy than there is today, as soloing anything above +0 or +1 was hard for everyone, except maybe Scrappers. But yeah, no travel powers till level 14. Capes weren't in the game till later, and even then you had to do a level 20 mission to unlock them. Spent a lot of time Hovering across Kings Row and the Hollows because it was simply too dangerous to Sprint to all those missions you got at the opposite end of the zone with all the purple critters. Level cap was 40 and PI didn't exist yet.
IMO, at least in terms of gameplay, I3 was perfection. I4 is when all the nerfs started, and I will die on this hill: ED broke the game. It was never the same (read: as good) after that. Jack never quite understood that playing superheroes should be a vastly different experience than playing D&D. It was a very difficult time, watching him slowly dismantle what was previously such a great game to play (I mean, it was still fun and I still played, but it just wasn't the same; you never really ever felt "super"). IOs came something like 2 years later, and one could theoretically make up for what had been taken away, but it required a LOT of grinding for INF and/or playing the market, and created a huge divide between the casual and hardcore players in terms of raw power, something the game still struggles with now.