Glad that you like it :-)

1. Regarding storage - The styles that you type are stored in "localStorage". When you are cleaning the history, you may just uncheck the "Offline Website Data" option in the "Clear Recent History".

2. Regarding taking too long to load - This is partly an issue from our end because the whole extension consists of so many different files. We can optimize it by bundling the most of the code into just a few files. The reason for not attempting that was the fact that using minified code would make the approval process for Mozilla extension store take longer time. I believe that Mozilla's extension approval process has now become a lot more automated and faster. We may now be able to attempt a fix for this problem by bundling the application code without adding much delay to the update/release process. Though it might take a little time before we make that change.