I did that, unfortunately the search feature in Thunderbird is just terrible compared to Mail.app (maybe there is a plugin I don't know about?)
If you're actually trying to encrypt email, you probably don't want your mail app building a search index in plain text.
Just getting a working subject / from / to search would be great. That said, my primary purpose with GPG is securing the emails in transit, not on my laptop. I already use disk encryption and most of the documents I send are stored unencrypted on that disk as well. The kind of people that would break into my computer would most likely just install a keylogger to get my GPG key rather than look for plain text indexes.
Depends if you're primary concerned with transit, vs local storage.
Yeah, it's a bit weird, but I usually just click "Display as List" on search results pane and then it becomes more usable...