Wrote their own GWT Serialization using SDATA (SDATA similar to GDATA).

XML UI def passed to Client which renders the "view".
But each page still has some custom code delivered to the Client.

Used Incubator Table, now moved to Cell Table.

http://css3pie.com/

Utilizing Hidden Fields (Top, Bottom, and some in the middle which were used to redirect tabs to newly enabled fields).

Use Client Bundles to reduce RTs during initial load.

Framework deriving and injecting Widget IDs for Selenium/Fitnesse.

Using versions in the URL to control GWT Version.  Users can configure when they switch to new versions by module.