I really like your plugin, but my blog was starting to slow down, so I decided to optimize it a little bit by starting to turn on define('SAVEQUERIES', true); and add print_r($wpdb->queries); in my footer. This lets me check all queries done to the database while loading my blog.
The first time I checked
404 queries in 5.390 seconds.
And a lot of them where on the options table at xxxxxx_transient_timeout_al2fb_cache_xxxxxxxxx.
So I turned off your plugin and checked a second time
159 queries in 1.490 seconds.
So I think that's a serious difference.
I hope you can fix this :)