This is the first full week that there are no champions I haven't tried out already. I started playing on the 9/4/2012 free rotation, but didn't get to all the champs before it ended. There have been about 200 free champion spots since then, and there are only 110 champions. Essentially, they could have all been in the free rotation twice in this span of time. I understand the repetition of champions, but not the complete omission.
I usually like to try champs out before I know if I want to get them. It seems counter intuitive that all the champs don't get rotated semi-regularly. I know some I were excited to play, but didn't enjoy as much as I imagined. And the more skill I get, the more I like some champions the second time around when I couldn't really figure them out the first time. If players don't have the chance to experience the less used or more complex champions, then it just creates positive feedback towards them being used less. Even with the limited refund option, it seems wiser to wait rather than to blindly invest in purchasing a champion, because you never know until you try it.
Really, each champion should show up in the free rotation at least once in (2*total champions)/10 rotations. Or ideally, at least .5% of the time, so that frequency doesn't decay as more champs are added. Right now that means 1 times free per 20 weeks, which is hardly unreasonable.
PLEASE start sticking these forgotten champs in rotation soon. /rant