I give it an 8, though really it's 7.5 rounded up. A very good romance show either lets you still feel for the couple even if that isn't exactly who you're rooting for (Kanon in my case), or makes you change the couple who you're rooting for (KGNE for me, countless times might I add), or just does a really good job in the 'feel good' department (Original To Heart). Shuffle failed for me in all three respects, which is odd because Shuffle is the only ero-based anime that i can recall in which I feel totally indifferent to the couple that 'won'.
Kaede and Nerine I can understand me feeling for them, as one is the childhood friend while the other is IMO the cutest girl in the show, but Sia as well? I think I would've enjoyed the show a lot more if they cut a little of Sia in the middle and put in a little bit more Asa, since no one can deny Sia had the most time in the show before the start of individual character arcs. If Asa had much more screen time in the beginning, rather than short snippets here and there, my score would be a lot higher. However, 3 out of 4 girls I can feel for? (Primula doesn't count, not much into lolicon XD) +2 points, since I rarely feel for girls other than the childhood friend.
However, Kaede arc was one of the most original and interesting (controversial even?) arcs I have seen in a while. Personal bias aside, no one can deny it generated the most discussion on Shuffle. Heck, it was so good it even made me doubt the Asa ending I was dreading, which I saw minor clues around eps 7 (was it?) and then I got dropped an anvil when I saw her encouragement being what gave Rin the courage to save Primula in her arc, which all but confirmed the ending to me. Keeping me guessing gives it a minimum of 4, but with Kaede's arc being so entertaining it's a 5.5 IMO.
For comparison's sake in recent seasons shows, I currently give Canvas 2 a 6.5. Sure it's still not done yet, and sure the couple I am rooting for seems to be winning (childhood friends to boot), but nothing so far is memorable. It's watchable and entertaining, but forgettable at the same time.
Suzuka on the other hand, I give maybe an 8.5, though it's still rising even when I only have watched the first 16 eps. At first, I couldn't get into the show, seeing as the title of the show is the name of one of the characters, which means it's pretty darn obvious who the guy is going to end up with (and not the one I was rooting for in the beginning). But after eps. 3, it doesn't matter knowing that. Remember the three criteria I mentioned in the beginning? So far, it's succeeding very well in all three, on top of the best lead character development I have seen in quite some time, something that is typical only of Shoujo manga/anime.
And since we're talking about it, I give Futakoi an 8. Very minor spoilers.
The next season though I couldn't get much into, as it turned more into an action show more than anything. I get my dose of action in games, as action anime pales in comparison to that IMO. Thus, I can't give it much of a score.