I'd consider some of them essential because they are likely referenced in old threads and emails (lostpw, terms, requestemail), others would be nice to have.
Code:
/login.php -> /login/
/login.php?do=lostpw -> /lost-password/
/memberlist.php -> /members/
/misc.php -> /help/
/misc.php?do=bbcode -> /help/bb-codes/
/misc.php?do=showrules -> /help/terms/
/private.php -> /conversations/
/profile.php?do=buddylist -> /account/following
/profile.php?do=editavatar -> /account/account-details
/profile.php?do=editoptions -> /account/preferences
/profile.php?do=editpassword -> /account/security
/profile.php?do=editprofile -> /account/account-details
/profile.php?do=editsignature -> /account/signature
/profile.php?do=ignorelist -> /account/ignored
/profile.php?do=privacy -> /account/privacy
/register.php -> /register/
/register.php?do=requestemail -> /account-confirmation/resend
/subscription.php -> /watched/threads
/usercp.php -> /whats-new/