How good are the open source Windows apps?

How good are common open source Windows applications, like Firefox, Thunderbird, and the newest, Sunbird (calendaring)?

Based on the feedback at Mozilla itself Firefox is OK (I use it for most applications), but Thunderbird still has some migration problems and according to a story in ZDNet UK yesterday Sunbird isn't ready for prime time.

The last should not be surprising. Sunbird is only on Version 0.2. But Thunderbird, like Firefox, is at 1.0.

Critics note that Thunderbird is a clone of Outlook Express, not Outlook, and I've found it wanting (although I'm ready to try it out again soon). Integration between Sunbird and Thunderbird, resulting in something more like Outlook, is due later this year.

To me, the real surprise is that, despite Firefox' rich feature set (tabbed browsing, easy-to-edit favorites, improved page search functions) we have yet to see a response from Redmond. How long are they going to wait, and what exactly should their response be?

But what I think doesn't matter much. It's what you think that matters. Have you made the switch to Firebird, or Thunderbird? Have you tried Sunbird? And what enhancements to your favorite applications are at the top of your wish list?

Let us know in TalkBack.