I use it for as much as possible, including navigating my source tree. Thus I have an alias, mirroring the OS X open command:
alias open=cygstart
Eg. open . opens the current directory in explorer and open README.txt launches Notepad++.
And I have a small script so that I can use tortoiseSVN from the command line, which I find invaluable. Bringing the best of both worlds together.
#!/bin/sh
# Use TortoiseSVN from the cli
# Public Domain, Max Howell 2008
path=$2
test -z $path && path=.
test -e $path && path=`cygpath -wa $path`
svn='/cygdrive/c/progra~1/TortoiseSVN/bin/TortoiseProc.exe'
function svn
{
"$svn" /notempfile /command:"$1" /path:"$path" &
}
case $1 in
up | update) svn update;;
ci | commit) svn commit;;
log) svn log;;
props) svn properties;;
browse) svn repobrowser;;
*) /usr/bin/svn $@;;
esac
Now svn ci opens up the Tortoise commit dialog, which is the best I've found on any platform. svn log opens the pretty good, but very useful Tortoise log dialog. Et cetera.
I maintain the script here: http://www.methylblue.com/blog/using-tortoisesvn-from-the-command-line/