The "new" Google Maps is essentially an opt-in beta. The "replacement" is to continue to use classic Maps until it is done. It is obvious that most of the old features like multi-stop directions will return, but Google needed external testers because WebGL is very dependent on machine performance and GPU, and they indicated as much when they limited the initial users to an explicit signup form.

I find the new Maps interface incredibly better than the old one. Search results appear directly on the map so you can see spatial relationships, easily highlighted and clickable. It invites exploration. No separate Google Earth plugin needed, seamlessly move from 2D to 3D, no separate Flash plugin for Street View. The way the map spotlights important roads and related places when you click on a particular POI helps with planning.

The only downside is it is slow, because it is a very complex web app, probably the most complex one ever written, but I'm sure they'll optimize it by the time it is ready for public consumption.