The second problem came with 1.3.2: half of all my subscribed feeds don't show up at all, because all messages are marked as read even the new ones.
http://www.stern.de/standard/rss.php?channel=politik
http://www.spiegel.de/schlagzeilen/rss/0,5291,,00.xml

Third problem, how to get to the options the easy way? Currently I have to go to the whole Tools->Add-ons thing or wait till the sidebar is empty to a popup menu with Options.

One suggestion, a "Show only x messages per feed" option ... please.

Leaks in window 0x18f3b540:
[+] [leaked object] (18f3b090) = [Object]
[ ] tree = true
[ ] progressText = true
[ ] previewPane = true
[ ] nextUpdateDisplay = true
[ ] strings = true
[ ] displayPeriod = true
[+] prefs (19000dd8) = [XPCWrappedNative_NoHelper]
[+] QueryInterface (19000dd0) = [Function]
[ ] prototype (4b7f3b8) = [Object]
[ ] addObserver (19000db8) = [Function]
[+] getIntPref (19052f40) = [Function]
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[ ] getBoolPref (19052408) = [Function]
[ ] root = true
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[+] clearUserPref (49c99c8) = [Function]
[ ] prototype (41c2988) = [Object]
[+] lockPref (49c9970) = [Function]
[ ] prototype (41c29e0) = [Object]
[+] prefHasUserValue (49c9898) = [Function]
[ ] prototype (41c2b10) = [Object]
[+] prefIsLocked (49c9730) = [Function]
[ ] prototype (41c2bd8) = [Object]
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[ ] prototype (49c8dc0) = [Object]
[+] getChildList (49c9700) = [Function]
[ ] prototype (49c8e30) = [Object]
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[ ] prototype (49c8e68) = [Object]
[ ] PREF_INVALID = 0
[ ] PREF_STRING = 32
[ ] PREF_INT = 64
[ ] PREF_BOOL = 128
[+] removeObserver (49c9610) = [Function]
[ ] prototype (49c95d0) = [Object]
[ ] feedsToLoad = 0
[ ] feedsLoaded = 0
[ ] updateTimer = 3
[ ] loadTimer = null
[ ] currentRequest = null
[ ] feeds (18f3ade8) = [Array]
[ ] feedData (18f3ade0) = [Object]
[ ] lastUpdate = true
[ ] nextUpdate = true
[+] init (18f3adc0, chrome://feedbar/content/feedbar.js, 57-96) = [Function]
[ ] prototype (42d1f90) = [Object]
[+] observe (18f3ada0, chrome://feedbar/content/feedbar.js, 99-120) = [Function]
[ ] prototype (3af8c68) = [Object]
[+] updateFeeds (18f3ad90, chrome://feedbar/content/feedbar.js, 124-138) = [Function]
[ ] prototype (3af94a8) = [Object]
[+] stopUpdate (18f3ad88, chrome://feedbar/content/feedbar.js, 142-144) = [Function]
[ ] prototype (4945190) = [Object]
[+] findFeeds (18f3ad80, chrome://feedbar/content/feedbar.js, 147-218) = [Function]
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[ ] prototype (40afae8) = [Object]
[+] setUpdateFrequency (18f3ad40, chrome://feedbar/content/feedbar.js, 333-334) = [Function]
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[+] setReloadInterval (18f3ad38, chrome://feedbar/content/feedbar.js, 337-355) = [Function]
[ ] prototype (40753f8) = [Object]
[+] checkFrequencyItem (18f3ad30, chrome://feedbar/content/feedbar.js, 359-369) = [Function]
[ ] prototype (4075bb8) = [Object]
[+] checkPeriodItem (18f3ad28, chrome://feedbar/content/feedbar.js, 373-383) = [Function]
[ ] prototype (4075c20) = [Object]
[+] history (18f3ad20) = [Object]
[+] hService (18f3acb0) = [XPCWrappedNative_NoHelper]
[ ] isVisited (190523b0) = [Function]
[-] QueryInterface (4bcfde8) = [Function]
[-] addURI (4bcfca8) = [Function]
[-] setPageTitle (4bcf680) = [Function]
[+] ioService (18f3ac90) = [XPCWrappedNative_NoHelper]
[ ] newURI (190523e8) = [Function]
[-] QueryInterface (4bd0ae0) = [Function]
[-] getProtocolHandler (4bd0460) = [Function]
[-] getProtocolFlags (4bd03e8) = [Function]
[-] newFileURI (4bd02f0) = [Function]
[-] newChannelFromURI (4bd02e8) = [Function]
[-] newChannel (4bd00e0) = [Function]
[ ] offline = true
[-] allowPort (4bd00a0) = [Function]
[-] extractScheme (4bcfe08) = [Function]
[+] URI (1968dfe8) = [XPCWrappedNative_NoHelper]
[ ] spec = true
[ ] prePath = true
[ ] scheme = true
[ ] userPass = true
[ ] username = true
[ ] password = true
[ ] hostPort = true
[ ] host = true
[ ] port = true
[ ] path = true
[-] equals (4b914c8) = [Function]
[-] schemeIs (4b913e8) = [Function]
[-] clone (4b913d8) = [Function]
[-] resolve (4b91378) = [Function]
[ ] asciiSpec = true
[ ] asciiHost = true
[ ] originCharset = true
[+] isVisitedURL (18f3ac88, chrome://feedbar/content/feedbar.js, 393-434) = [Function]
[ ] prototype (4b7e460) = [Object]
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[+] onTreeClick (18f3ac70, chrome://feedbar/content/feedbar.js, 471-569) = [Function]
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[+] markItemAsRead (18f3ac68, chrome://feedbar/content/feedbar.js, 573-595) = [Function]
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[ ] item = true
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[ ] prototype (5026ae0) = [Object]
[+] openAll (18f3ac08, chrome://feedbar/content/feedbar.js, 904-919) = [Function]
[ ] prototype (4fd6db8) = [Object]
[+] openFeed (18f3abf0, chrome://feedbar/content/feedbar.js, 924-939) = [Function]
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[+] markAsRead (18f3abe8, chrome://feedbar/content/feedbar.js, 944-949) = [Function]
[ ] prototype (4fd7668) = [Object]
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[ ] prototype (4fd8768) = [Object]
[+] unsubscribe (18f3abd0, chrome://feedbar/content/feedbar.js, 980-986) = [Function]
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[+] addError (18f3abc0, chrome://feedbar/content/feedbar.js, 1035-1037) = [Function]
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[+] notifyCallback (18f3aba0, chrome://feedbar/content/feedbar.js, 1089-1093) = [Function]
[ ] prototype (1d964d0) = [Object]
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[+] launchUrl (18f3ab78, chrome://feedbar/content/feedbar.js, 1124-1132) = [Function]
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[+] _addTab (18f3ab70, chrome://feedbar/content/feedbar.js, 1136-1150) = [Function]
[ ] prototype (173bc58) = [Object]
[+] _inTab (18f3ab68, chrome://feedbar/content/feedbar.js, 1154-1155) = [Function]
[ ] prototype (173bc68) = [Object]
[+] getDB (18f3ab60, chrome://feedbar/content/feedbar.js, 1158-1168) = [Function]
[ ] prototype (14a3778) = [Object]

Also cool would be:
- A lower limit than "last day". At best, configurable.
Or maybe even some sort of folder structure you can define (eg. one folder for last 4 hours, today, yesterday, ...)
- Right click on feed => "Update this feed"
- Option to only show feeds from a special folder
- Favicon instead of folder for the feedlist
- Some green dot or something that indicates "hey, look! new stuff in this feed!" that disappears when you opened that feed.

(Firefox 2.0.0.12 on Windows Vista.)