I remember a few things.
Firstly, being puzzled at how they managed to fuck up so totally in so many different ways despite virtually everything having leaked beforehand and despite Microsoft knowing, with absolute certainty, that the internet hated their plans. Before the reveal, when it became obvious that they really were so utterly fucking stupid that they were going to require internet check-ins to run your own discs, the only defence Xbox fans mounted was that the idea was so stupid that it couldn't possibly be true. The specs were puzzling as well - it took a while before the exact difference could be nailed down, but it was quickly obvious that there was going to be a noticeable difference in Sony's favour.
Secondly, just a total disconnect from the Xbox brand, the most jarring decision being the one to shove an expensive motion camera into every box just because Kinect sold well for a few years. The reveal wasn't just US-centric, it was a showcase of a product that made it clear that during the design phase, nobody had given a moment's thought to the world outside the US. From TV integration that literally couldn't work in more than a few countries, to a snap mode made by people who forgot that 50Hz was still the broadcast standard for most of the world, to the stultifying stupid idea of splitting up European launch dates between countries.
Thirdly, amazement as the whole mess dragged on for a month. From reveal in May to an E3 where they knew that they had to address the criticisms but did not even make the slightest effort to do so, to the point a week after E3 where someone finally made them begin to realise how stupid they were being and that they had to back down. Even then they only fixed the disc-locking, forced internet checks and per-country region locks - they still did nothing about Kinect or the staggered European launch.