When you install a .src.rpm, you do get something installed, but not in the way you expect if you're new to rpm's. A .src.rpm installs two files: a spec file in /usr/src/<distroname>/SPECS, and a tarball in /usr/src/<distroname>/SOURCES. When you run rpm --rebuild, your binary rpm will be written to /usr/src/<distroname>/RPMS/arch/i386.
The rpm --rebuild command gives you an installable binary, and should install the binary (according to the man pages, anyway). But, I've never seen the binary installed, only written to the above name directory. I then had an rpm to install. That may be a variation on rpm done by certain distros (controlled by a script somewhere, maybe?). It's a minor hassle for me. I'd rather do it that way anyhow. Build it now; install it after i've had a chance to test it (rpm --test). Hope this helps.