thanks for trying the new Exhibit result format. As you stated correctly, some features are still experimental.

Based on the few examples I could find, and the scattered documentation, I am currently stuck in two dead ends :

I am currently compiling some documentation. In general I decided to change a part of Exhibit's syntax to align it to the wiki environment. Thus, the existing documentation of Exhibit is not applicable in some cases.

1- Did anyone figure out how to use the 'lenses' aspect of the format ? I had no luck so far based on Exhibit and Wibbit documentations. In particular, I am looking for color coding a row or embedding URLs in a tabular view.

The Exhibit result format employs the MediaWiki template system for defining lenses.
To advise Exhibit of the MediaWiki template it is supposed to use, you have to add the parameter lens=templatename to your query. Please note that the name of the markers in the template (e.g. {{{markername}}}) have to match the name of the properties Exhibit is fed with. 
At the moment lenses are just applied to the tiles, map and timeline view and therefore have no effect on tabular views. 
2- Is there an example of Timeline facet available somewhere ? I created a start, end, proxy and colorkey attributes, and all I get is a javascript error (Unable to create a Timeline).

In most cases the start parameter is obsolete, since Exhibit accesses SMW's information about data types. If a property of the type date is present, Exhibit automatically creates a timeline that is based on this property. To override this procedure you can set the start parameter manually: start=dateproperty (no prepended dot). In terms of the date format Exhibit is kind of restrictive, but it should work fine with SMW's built-in date type. The JavaScript error points towards the fact that Exhibit has trouble parsing the date format.