My Windows e-mail, news and RSS client of choice, Mozilla Thunderbird, reached 1.5 release status today. I just installed it, and it seems to work fine. There are no immediately-visible changes when you first start it up. The Options dialog is of course now similar in style to Firefox 1.5, and the extension update mechanism is also inherited from Firefox. The Manage Subscriptions dialog has been extensively updated – you can now import OPML files, and create folders for your feeds, which is a big benefit. I guess I have to spend some time reorganising my subscriptions.
Unfortunately quite a few of the extensions that I use are not currently compatible with 1.5 (NestedQuote Remover, Signature Switch, Move Search Items, View Headers Toggle Button, and compact folder), but hopefully they will get updated soon.