Just for fun, I ordered this SMA tool in Hong Kong
VMA, a well known spectrum analyzer specialist, wrote an alternative software, you can find more details on his blog.
http://vma-satellite.blogspot.pt/
and for less than 60 euros, believe me, the spectrum is not so slow !
The waterfall is include (only available and expensive analyzers)
few screenshots of my 1st test today
The Simple Spectrum Analyzer by Vitor Martins Augusto (VMA)