I believe I might have used 7.5 and 8.5 if they had been available to differentiate a little more in the 7-9 range. But already a 10 point scale is a lot.. If I had given out 7.5's and 8.5's, they wouldn't really be that accurate. When I look at my votes, sometimes I feel that I should lower votes of some animes and raise those of others, while at other times I feel about the exact opposite.
What's wrong with 3 star scale? 5 star? 7 point? 10 point? 100 point?
Obviosly with 3 star scale you're only going to get three kinds of results. You're not going to compare good anime to another good anime - they both got 3 stars for being good.
On 5 star scale you'll have "great" added over three stars (and "bad" below "not good"), and can fan out the votes a little more.
I believe 7 point scale would be close to optimal. Would leave 5 => 4, 7 => 5, 9 => 6, 10 => 7 on the upper end. If something is better than "not bad, not good", is it already good enough to recommend? I've used 6 for cases where eg. I've got a few good chuckles out of something but that's it. That anime would live just as well with 5 - it wasn't good enough for me to tell someone else about it. And 8 is just for those of the upper end of 7 that you don't think deserve a 9 - that is, you don't start harassing people about them until they watch them, but are the first ones you'd recommend to people after they've seen everything you've forced upon them (10's and 9's).
10 point scale is what we have now. It's not balanced symmetrically but rather there are more grades on the positive than negative side. For me, this is just fine - if I don't like something, I'm not likely to watch it to the end unless it's short. And if I don't complete it, I won't give it a permanent vote - how could I not having seen it completely? Still, I think there are more than enough low grades.. Doing away with one of them would be just as good. Even just two grades below "not good, not bad" would be fine: "bad" and "hate it".
So, how about grading systems with more choices - like 19 point grade (1-10 with half-points)? I doubt the low half-points would be of any use really, so it would add a lot of useless grades on that side.. In the mid-grades (4.5 & 5.5) I doubt it'd make any difference. If it wasn't good or bad, would I /care/ enough about it to try to compare it against other "not good, not bad" animes to differentiate them by half-points? And as I noted, in the good to great area, the half points would depend on my mood and I'd just want to shuffle them around forever, sometimes feeling that something is rated too high or low, while at other times wanting to reverse my changes again. In the extreme high it might make a difference: 9.5 would probably be even useful..
100 point scales? You know how they are.. the lower order digit is quite random and useless
So, summarizing my opinions:
7 points is minimum to work with, 10 points may have some problems but gives a few more grades to work with, more than that and differences by one grade are mostly meaningless. Thus, the 10 point scale we currently have is likely the best compromise.
And yes, most votes will be in 6-9 area. Most of us like most anime and thus will give at least "fine" for them, and most of us want to keep 10's in some check.
What I would like to get is a per-user vote distribution. A graph on my vote page showing how many of each grade I've given - one just like that on anime rating pages, but containing all my permanent votes instead of all users' votes on one anime. After that, start eliminating influcence of users based on their vote graph: if your vote distribution diverges too much from "acceptable" distribution, none of your votes will be used to calculate anime ratings.
