Other sites say that umfpack is faster than superlu, but do nothing to
back it up.
Matlab 6.5 uses umfpack for its sparse solver and arpack for eigenvalues.
arpack++ is a C++ library for sparse matrices which can already call
superLU and umfpack. I haven't looked at it in detail, so I don't know
how much work it would be to turn it into an octave value, or even what
license it is released under.
A recent TOMS article gives a sparse blas reference implementation. Andy's
sparse ops have these as C++ macros. I don't know if it is worth changing
to using sparse blas.
Unfortunately, none of this investigation got me anywhere closer to
releasing a 2.1.40 compatible octave-forge. Oh, well!