I run Thunderbird on Ubuntu Linux. I have Mail Toolbar, Menu bar, and Status bar, checked.
I do like how TB now will detect if the message is from a "list". It was maybe a year ago that "Reply List" showed up, or the first time I remember seeing it.
There are still people out there that forget and use Reply, which was the way to reply to the list's emails before the new button showed up.
I have used TB on Windows, but I do not set my Windows systems to read my email accounts that I use on my Ubuntu system. Do not want to read/reply to emails outside of my default system, just in case I forget about one.
The only trouble with TB right now is the fact that the Status bar no longer tell me which accounts it is looking at for possible mail needing to download. Yes, I have a few - 18 with my GMail included that are read through TB. I have a few web-mail only accounts that I tend to forget about, since I rarely ever use them.