I seem to have run into the same problem. The options table in the DB of one of my sites has bloated to nearly 60 MB which I would expect to be about 1 or 2 MB max. It's not a large site, the posts table is about 2.3 MB, and it's hosted low budget. The size of the options table now effectively breaks the site because the DB size has gone over the allowed size of the low budget provider.
Speed is nice but if one day it is going to break your site up like this, I don't see the advantage. A ticking time bomb...
Or is this bloating an indication of some faulty plugin? I've yet to find the plugins that is causing all these transient entries.
From the API documentation I gather these entries are temporary but who/what will actually take care of clearing expired ones form the database? Should WP be doing this or is it left to the plugin that spawned all of them into the DB in the first place?
Thanks for any info on this subject :)