I have tried/used pretty much every email client in existence (remember when Pine was like gold?) I've found that the biggest issue -- even beyond the UI is the ability to easily get mail in and out of various clients if you want to switch. I was a sworn Thunderbird user then switched to Mac Mail only to find that the file formats were different. The same goes for Outlook etc, with email, the data is what matter I have tried/used pretty much every email client in existence (remember when Pine was like gold?) I’ve found that the biggest issue — even beyond the UI is the ability to easily get mail in and out of various clients if you want to switch. I was a sworn Thunderbird user then switched to Mac Mail only to find that the file formats were different. The same goes for Outlook etc, with email, the data is what matters, not the app. Odds are I will switch to Thunderbird again if the next version of Mac Mail is as lame as this one. And yet, I long for an integrated suite… Via Wired News: WN: What advantages does Thunderbird offer that a web-based app like Gmail doesn’t? MacGregor: Some users want to have their data local for privacy and control. Furthermore, you can integrate data from different applications on the desktop in ways that you can’t do with web-based solutions, unless you stick to web solutions from a single provider. For example, you can use your Outlook address book with Thunderbird. We’d like to continue to expand the kinds of data you can share between Thunderbird and other apps (both web and desktop applications). Open Source