Playing around with npm's semver, most of it seems to translate well to the npm CLI, e.g.:
npm install somepackage@~1.0.0-rc
... will include everything greater than the 1.0 version in the same minor range.
But to include a greater than symbol, e.g.:
npm install somepackage@>=1.0.0-rc
...it blows up the shell because it thinks I'm trying to output to file. I tried wrapping the version in quotes and several other options but to no avail.