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I didn't install it on a new profile, but i keep mine pretty spiffy. Brief seems to ignore the fact that AIOS is installed and uses it's own sidebar instead. Didn't like that at all, especially when AIOS is so incredibly popular. I found the toolbar button to be in the wrong state sometimes (Brief open, button not depressed). Worst of all, i fed it my RSS directory and... nothing. Didn't list any feeds in any subfolders. ByeBye
1) The lack of integration with AIOS is expected, because Brief's sidebar is actually placed WITHIN its tab. This way the sidebar is permanently associated with the tab, so you don't have to hide the sidebar manually when switching to a different tab, closing it etc.
2) The toolbar button not staying depressed is a really minor issue and it's going to be fixed in the next release.
3) I'm sorry that Brief didn't work for you but it certainly wasn't something that couldn't be resolved after some investigation, so rating it 0 right away seems a little harsh.