An example how to use greek utf enconded text letters, like τ,Γ,π,ω…, as direct input method in latex instead of $\tau$, $\Gamma$, $\pi$,$\omega$… . Each letter requires a newcommand in the preface.
PDF: greek_unicode.pdf
Files: greek_unicode.zip

Latex Code
\documentclass[10pt,a4paper]{article}
\usepackage[utf8x]{inputenc}
%small letters
\newcommand\textalpha{\ensuremath{\alpha}}
\newcommand\textgamma{\ensuremath{\gamma}}
\newcommand\textpi{\ensuremath{\pi}}
%capital letters
\newcommand\textGamma{\ensuremath{\Gamma}}
\newcommand\textPi{\ensuremath{\Pi}}
\begin{document}
Formula using Latex standard math environments versus unicode:
\begin{eqnarray*}
\mathrm{latex input} & & \mathrm{unicode} \\
\alpha & \Leftrightarrow & α\\
\gamma \Gamma & \Leftrightarrow & γ Γ \\
\pi \Pi & \Leftrightarrow & π Π
\end{eqnarray*}
\end{document}
Hypperref Problem
When the hypperref package is used additionally some greek letters cannot be defined via the \newcommand anymore, such as \textmu and \textbeta. The error looks something like that
! LaTeX Error: Command \textmu unavailable in encoding OT1.
! LaTeX Error: Command \textbeta unavailable in encoding OT1.
A workaround is to remove the error causing commands and load additionally the tipa package and the textcomp package, that will do the trick.
\documentclass[10pt,a4paper]{article}
\usepackage[utf8x]{inputenc}
\usepackage{hyperref}
\usepackage{tipa,textcomp}
%small letters
\newcommand\textalpha{\ensuremath{\alpha}}
\newcommand\textgamma{\ensuremath{\gamma}}
\newcommand\textpi{\ensuremath{\pi}}
%capital letters
\newcommand\textGamma{\ensuremath{\Gamma}}
\newcommand\textPi{\ensuremath{\Pi}}
\begin{document}
μ, β, α, γ, π, Γ, Π
\end{document}