Geoff,
The "Watch document" command should attempt to use gv as the previewer, in latex mode. (I haven't tried this for a while, but it used to work and could easily be fixed if it's accidentally been broken.)
That's much faster than generating a PDF. As you've probably noticed, converting PostScript to PDF is actually the slowest part of the process, for a long or complicated document.
"Watch document" also caches the processed version of the document preamble, so you should find it significantly faster to update when making incremental changes.
Robin