Solaris (9):
    strftime() doesn't recognize the default '%s' time format. I'd rather keep
    this default for other OS's. If your running Solaris, you can change the
    default time format in config.h after running ./configure or specify an
    alternate time format with the -t command-line option.

NetBSD (1.6.1):
    The lastlog hostname length is limited. It seems to be still using utmp
    rather than the newer utmpx. The utmp options are using utmpx though. This
    is true for the system I was testing on. It may be using utmpx on yours.

    Login process id gotten with KVM is untested on this OS.

src/mail.c:
    Included files, subgroups and 'user@host' format in the mail alias file aren't
    considered.

src/login.c:
    WTMP support? For example: -O login.so -#3 would return the 3rd last
    login. I haven't implemented this do to system performance issues. More of
    an would-be enhancement than a bug though. :)