I have a document full of matrices, and many of them don't look very good, right now. Hunting for solutions, I found this post from two years ago.
I have the same problems mentioned there, and I'd also like to have better control over the amount of space between the outer-most columns and my delimiters (which are either brackets or lines). If it matters, my matrices are always either 3x3 or 4x4.
Has any progress been made in the last two years?
I would think that this would be a very common problem, and I'm amazed that there doesn't seem to be a package that addresses it.
Added
Two of the three problems I mentioned are well illustrated in the post cited above, so I don't see any point in repeating them here.
The third problem I mentioned is shown here:

I'd like to have more space before the first column and after the third column. The example above was produced with the following code
\documentclass[a4paper,10pt]{article}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{mathtools}
\usepackage{fontspec}
\setmainfont{Latin Modern Roman}
\begin{document}
$$
\begin{bmatrix*}[r]
{1} & { 2} & { \mathbf M} \\
{1} & {-3} & { \mathbf M} \\
{1} & { 6} & {-\mathbf M}
\end{bmatrix*}
$$
\end{document}
I can fix the matrices one at a time, but that doesn't seem like the right solution. I'd like to have a new "matrix" command, but I don't have the expertise to create this myself, so I'm hoping that there is a package that provides one, now, after 2 years of progress.
Attempt at a Solution
Here is a neophyte's attempt at a solution, based on the one from Gonzalo Medina in the post cited above:
\newcommand\myfact{}
\newenvironment{Mybmatrix}[2][1.8]
{\renewcommand\myfact{#2}\renewcommand{\arraystretch}{#1}\left[\;\begin{matrix}}
{\\[-\myfact em]\mbox{}\end{matrix}\;\right]}
I don't understand much of it. Is this a good approach?
arraypackage, define aLeft andRight column as follows:\newcolumntype{L}{@{\hspace*{4\arraycolsep}}c}and\newcolumntype{R}{c@{\hspace*{4\arraycolsep}}}. This will give you 4 times the gap on either side of the matrix, between it and the delimiters you use. Then use\left(\begin{array}{L..R}...\end{array}\right). – Werner May 02 '13 at 06:39amsmathis exactly to remove the bad space between the delimiters and the first and last column. – egreg May 02 '13 at 10:50