The new Bing Maps Ajax control is just a third of its former size. How does it achieve this? By starting over with a new, non-compatible, design.
Microsoft has released a new version of the Bing Maps Ajax Control - V7. Its main claim to fame is that it is more efficient. It also claims to be 1/3 of the size of the previous control and up to 3 times faster. In addition, it is able to make use of HTML5/CSS3 where these facilities are available by dynamically detecting browser capabilities and using them where possible.
The new API now allows access to the enhanced "Birds eye" view and the new map style introduced recently is now the default. It is also optimised for mobile use including touch support. Touch events now work without any additional effort.
The downside is that the API looks very different and it isn't backwards compatible with the previous version. It also leaves out many of the features such as the popup description associated with pushpins.Similarly many of the function calls that used the REST API are missing and you will have to write your own replacements. Layers are also missing, but the EntityCollection object does more or less the same job.
Converting to the new API isn't difficult but any changes are extra work. In this case the performance gain, especially for mobile devices, does seem worth the effort. More of a challenge is making up for the missing resources such as the popup infoboxes associated with pushpins. The control may be lightweight but this leaves more for the programmer to do.
Overall however the pain is worth the gain. Bing maps has finally forgotten its origins in Virtual Earth.
More information from:
Bing Maps Blog
You can also download an SDK help file for V7 from:
Getting started with Bing Maps AJAX Control 7.0
Getting Started with the Bing Maps Silverlight Control
Getting started with Bing Maps (Virtual Earth)