I used to hate Thunderbird. Is it better now?

This post is for people who've used the Mozilla Thunderbird email program, and are fairly demanding. Because I'm a demanding email user, and I'm considering Thunderbird.

But when I've tried it I've hated it, and I wonder if it's improved. A lot.

Background:

The other day I asked for help on improving my email situation. I got great advice, and I'll be moving to Google Apps, as several suggested. Tom Iglehart, co-chair of CCTWG, will help me with the move.

Here's the geek part: I currently use Outlook Express, but Tom points out that if I move to an app that supports IMAP, I'll be able to view all my emails (received and sent) from any device or any computer. (Why do I care? Among other things that will let my wife comb through email conversations about speaking engagements etc, which will take a big burden off my sole-proprietor plate. She's infinitely better than me at detail work.)

The best known app that supports IMAP is Outlook. I hate it. In my experience (three times over the years) it gets full and then it starts malfunctioning, and I'm not interested in putting in the effort to become expert at managing a dysfunctional program.

Several times I've tried using Mozilla Thunderbird instead. It was funky but okay, but there were infuriating limitations (really dumb missing features), which caused me every time to punt it and go back to Outlook, because my employer required it. Now that restriction's gone.

So I need to know, is Thunderbird a lot better than it used to be?