I recently ported my app back to the old Javascript API; I wish I could say that it was for the superior older documentation, but it was actually because the new API randomly stopped returning my calls from time to time. All of the big moneymakers' apps are built on the older stuff, so I figure when it breaks, it gets a bit more love. The documentation is still shoddy, the Bing-powered documentation search is abysmal…
There still is a preferred developer program for the bigger companies out there but it doesn't really offer much of anything. Go back a year though and it was a big benefit.