[DaveBlake]

I have two issues with the addon:
1) If I use allmusic.com to fetch ratings, the points are between 1-5 and so the number of stars shown is max 2,5 in Krypton.

Having done some testing I can not repeat this issue. I set allmusic as the rating source and see ratings > 5 both in the DB and on screen. Sorry Olympia if I sent you off on a wild goose chase!

You @Boulder you mention "number of stars" not a number, what skin are you using? I am wondering if the issue is the skin translation of number to stars. Switch to say Confluence (something that shows a number on album info dialog, Estuary doesn't show much at all) are the numbers wrong?
 

2) I'm unable to change the rating to be fetched from Musicbrainz. I tried removing my music source, cleaned the library, changed in the addon settings that Musicbrainz is used and readded the music source to scan. Allmusic.com was set for all albums

I can't reproduce that either. Changing the addon settings, and scraping music that has not been scraped before (and does not have album.nfo files) picks up the rating from the source in the scraper settings.

I can only wonder if you have album.nfo files?

If I try to change the information provider in the album list, it only affects the selected album and not all of my albums (even though I confirmed that I want to change all).

To clarify, yes that part is the known  bug.