The significant changes since release 0.83 are listed below (and a number of bugs in the release candidate for 0.84 were fixed).

New Functionality

Fundamental additions

Low-rank Cholesky up-/down-dating (CholMod)
Rank-one updates to LU factorizations (LUMod)
Added Generalized RQ and QR factorizations and associated General Linear Model (GLM) and Equality-constrained Least Squares (LSE) solvers
Pseudospectral computations can now be driven by various kernels, including
multi-shift Hessenberg/(quasi-)triangular solves. There is also now support a
variety of configurations for outputting snapshots of the results
Multi-shift Hessenberg solves (MultiShiftHessSolve)
Multi-shift quasi-triangular solves (MultiShiftQuasiTrsm)
Quasi-triangular solves (QuasiTrsv/QuasiTrsm)
Hyperbolic Householder transforms
Basic support for a block version of DistMatrix (BlockDistMatrix)
Support for parallel Schur decompositions via ScaLAPACK's Hessenberg QR algs.
Support for redistributing between DistMatrix and BlockDistMatrix [MC,MR] dists.
All user-level routines now use permutation vectors instead of pivot vectors
Alternating Direction Method of Multipliers (ADMM) implementations of Basis Pursuit, Linear and Quadratic Programs, and Sparse Inverse Covariance Selection

Added {lq,rq,qr}::SolveAfter
Added SymmetricSolve and HermitianSolve
Support for converting real (quasi-triangular) Schur forms to complex
(triangular) form
Support for computing the eigenvalues of quasi-triangular matrices
LQ/QR/RQ factorizations now force positive (or zero) diagonal entries in the
resulting triangular matrix
Grid now supports both row-major and column-major orderings
Support for diagonal scalings of trapezoidal matrices (DiagonalScaleTrapezoid)
Added Global{Col,Row} and Local{Col,Row}Offset member functions to DistMatrix
Norm and Max now support more data distributions
Min and Max implementations (which do not use the absolute values)
Added Bull's Head, Hatano-Nelson, random Helmholtz Green's, Trefethen,
Triangle, and Whale matrices.

Fixed several small memory leaks in Grid
AbstractDistMatrix::Empty() now recomputes shifts to ensure the matrix is kept
in a legal state
Moves of non-views to views are now converted to copies
Fixed deflation bug in PMRRR when no eigenvectors are requested
Fixed bugs in ApplyPackedReflectors, QuasiDiagonalScale, TriangularInverse, Trr, and Trsv

Algorithmic options are now handled via control structures with default
constructors
Preprocessor definitions and macros now namespaced with "ELEM"
Grid argument to DistMatrix::[Locked]Attach was moved before the dependent
alignment arguments
Added a 'Mod' routine which supports modular arithmetic with negative integers
Copy assignments now return non-const references
Move constructors are now "noexcept"
Checks were added to ensure DistMatrix views are not improperly aligned
PMRRR (and therefore Elemental) no longer requires a Fortran compiler to build
Renamed "ShiftedTrsm" to "MultiShiftTrsm" and placed in BLAS3
Renamed "Min" and "Max" to "MinAbs" and "MaxAbs"
Renamed "Inertia" to "InertiaType" and "HermitianInertia" to "Inertia"
The unnecessary Orientation arguments were removed from QuasiDiagonal{Scale,Solve}
All interfaces now assume the usage of 'left' diagonals, which use an offset relative to the diagonal which contains the upper-left entry

The python interface was removed due to SWIG's lack of C++11 support,
the lack of a maintainer for the interface, and the fact that a manual
C interface is planned.