I've used many, but that's ancient history. For a long time I used webmail and only Thunderbird in recent years. News of an interface revamp were scary, but so far no serious breakage. I guess people's complaints are about very heavy mailboxes or, most likely IMAP.

That is a different way of thinking: email as sort of a database of personal information, integrated with calendar and contact manager. If you're like me, only mail and not a lot of it, Thunderbird will be probably fine.