Without question, Google Web Elements are going to be a smash hit across the board. To have the ability to easily add in news, maps, even customized comments or a calendar with the Google juice at the helm is a pretty exciting prospect indeed.
Sadly however, Google Web Elements are not totally fool proof. Some blogging platforms just are not designed to play well with this type of scripting which will translate into a ton of forum posts from people frustrated as to why their elements are not working as well as expected.
With any luck, there will be a smoother way for those problematic blog platforms to enjoy the obvious functionality of Google Web Elements here in the not too distant future. After all, the technology is clearly sound. It is just a matter of finding some common ground for the blogs to present the content.