A couple of bugs seem to be common and I believe I have a workaround for them.
If Mail.app is crashing or freezing while scrolling or the WideMail column will not stay between mailbox switches try these options:
Delete the WideMail prefs located at: ~/Library/Preferences/com.daneharnett.widemail.plist
where (~ is your home directory)
WideMail has a problem with “messages with blank subjects” to rectify this add a character or extra token to the line that contains “Subject”.
Hopefully this helps everyone and I’ll be working to fix these bugs in the near future.