The purpose of the Log Browser is twofold. The obvious one is to give an example of how to use mod_sqil. Logging with mod_log_sql is simply the easiest way to get a database with a reasonable amount of data. It also demonstrates that you can get quite far with a pure REST approach without any server side state. The server only does data transformations. All view state is in the URLs.
The main problem currently is that XSL is IMHO not suitable for application development. It is even less suitable for the upper presentation layer (a.k.a. web design). Unfortunately there is no alternative at the moment. I hope to build mod_tal with XPath as its expression language someday, but by now there is no easy to use templating engine.
If you take a closer look at log.sqil, you will see that the same WHERE conditions are repeated several times. An include will be added to fix this. Looking inside the navigation tag you will also see, that for the more complex features the SQL has to be quite smart.