This thread actually prompted me to make my first post on the Riot forums.
As a new player (a few weeks) I have to say that I thoroughly enjoy the rotational system. It seems that Riot has included a good mix of classes and difficulties in the free champ selection (for instance, this week Anivia is included and apparently she's incredibly difficult to play). Each "week" I don't really know what I'm going to have available, and to me, that's a cool thing. It's a surprise. Thus, I was pretty pumped when Heimer was free this rotation as I had been looking to play him. I'm also looking forward to Mordekaiser, too. Think you can slip him in soon? :P
I tend to gravitate towards one or two champs each free-rotation, so I don't try them all, but that's because of personal preference. I start learning one and get the hang of it, like it, and practice with it. I think I went Nasus, Twisted Fate, Veigar, Sion, and now Heimer. Maybe I'll give Amumu and Ashe a whirl.
Basically, Riot, you're going to have a lot of haters no matter what you do. I just wanted to chime in and let you know that at least a few people like your rotational layout. Thanks for the chance to play and practice on free champs while we build up our IP. Although the rate of build-up is quite slow... are regular matches much more beneficial in terms of IP income? I've just been doing practices.