There are also a ton of people who are really impressed with the new software. The inline editing in the Standard editor is far better than the old version, with a lot of key combinations supported that weren't supported before. That's the main improvement I notice. I also love the fact that editing an existing thread now happens in-line instead of swapping to a separate editor page.
Note that the changes to the Search and the New Posts functionality has little or nothing to do with the new version. It is a practical decision being made by the webmasters to offer different functionality from the standard vBulletin functionality, because the The DIS has become too popular for the vBulletin functionality to work in a high-performing manner. They've engaged BoardTracker to make up for this limitation in vBulletin. It is actually a very common trade-off in systems design: Add latency; improve performance. While it would be nice if vBulletin's own software worked in a high performing manner with such a popular site like The DIS, it doesn't, and sometimes all the money in the world (assuming they had that) cannot make something work better.
I don't think there has ever been a system update that hasn't had at least some people complain. People like to complain, and people hate when things change. It's natural.
