new blog templates and _transient_ wp options

ok. love this plugin, but just noticed a couple things (some of these not limited to new blog templates plugin)

wp 3.0.2 multisite / subdomains, bp 1.2.6

1. i noticed that my database was over 40mb, with only like 30 subblogs and decided to investigate to see if this was normal. found that all of my subblogs had wp_options tables of over 1mb in size. thought that was strange. looked into it. there's tons of these _transient_ entries. so on a test subblog, i deleted them all (_transient_ of various types including "_transient_timeout_...", "...feed_", "..._plugin_slugs...") and the wp_options table reduced in size to several hundred k. much better! BUT, it seems these transients come back. what are they?? are these necessary? if not, how do i stop them?

2. in addition to the transients, wordpress keeps many plugin/theme options even after uninstalling them. realize that the new blog templates probably can't go and delete these orphaned options, but just thought i'd point it out to newbies using this plugin. you have to go in and carefully delete the unused options, so they don't get copied over to all new blogs. i don't think this adds much to the db size compared to the transients, but still...

anyway, my main concern is the transients. also, i simply deleted them all and everything seemed to work fine... but if anyone has a good reason why i shouldn't delete CERTAIN transients please let me know. thanks!