I thought it could be interesting to see in which order you all would rank Amy's producers. I'm biased towards pre-Blake era so my ranking might be somewhat peculiar.
1. Remi One of my very favorites among contemporary music producers. His beats+bass are dope. A very talented musician as well. His work with Amy is obviously one of the most important collaborations in music history ever! I also like his stuff for Ini Kamoze, Fugees/Hill, Nas, Left Eye, Ms. Dynamite, Chrisette Michele, Jazmine Sullivan, Tamia and also his solo stuff. He's so versatile. The main producer of my favorite album ever - Frank. Love him!
2. Williams His production credits for Amy only includes 4 songs (+bits and pieces), but those are some of my favorite musical moments ever. Dope beats. Just flawless magical stuff!
3. Hogarth Only one song but I absolutely adore everything about it (unlike Amy herself apparently). Love his Duffy tracks.
4. Ronson The collaboration which everyone talks about - The Legendary. It also completely overshadows the rest of her catalog among non-fans, unfortunately. His stuff with Amy is GOLD (except for the sound quality which is most likely due to the mixing). I'm not really a fan of his other stuff, with the exception of Paul McCartney, Lily Allen and Aguilera.
5. Howard Close To The Front - another song I adore. Fair production - but the awesome vocal arrangements makes up for it. He's a co-producer on Frank (songs based on his demos) which is why I have to rank him quite high anyway.
6. P*Nut A co-production credit. Production-wise it's my favorite Ronson track on B2B. It owes a lot to the original sampled song.
7. Rowe Do Me Good sounds unfinished (after all, it's an outtake). Amy's cute vocals makes it dope anyway. The same goes for 3xAmy, were she sounds incredibly sexy. There's nothing terrible wrong with the production but it's nothing special either. To flavourless and pop-ish/simple perhaps.
8. Simm: co-produced Close To The Front + Someone to Watch Over Me. Hard to rank since I don't know how involved he was. I like both tracks.
9. Rockstar Was he the guy who added the infamous strings to Take The Box? In interviews, Amy identifies the "strings-guy" as the one who mixed the track, which would be Elmhirst. Anyway, Amy strongly disliked the "additional production" for this song so I have the rank him at the bottom. I agree with her, the strings are superfluous.
[X. Amy One could argue that Amy herself should be on top of the list. After all, her whole catalog is primary her creation anyway. There's only a few early tracks where she didn't have the final word.]
Note: In some cases, it's hard to figure out the production credits as different sources gives different credits. There might be some errors.