I don't have any experience with iTunes, but the ripping speed may not be directly linked to your computer speed. I've found that especially the CD read speed dictates the time needed. Also there is a difference between ripping directly to an MP3 file, and via an intermediate WAV file. If the program you use normalizes the MP3 file, it can only do so via a WAV file. The total time needed will almost double because of this. Maybe iTunes does this automatically for you.
If you want to compare ripping speeds, you could download Audiograbber which is a free MP3 ripping utility:
http://www.audiograbber.com-us.net/
From the download page you need both the program and the LAME encoding DLL file. Install the program and copy the DLL file into the same directory and you're good to go!
Have a go with that, try some of the settings and see if it makes a difference!