I've been using Protools for mastering a number of projects - both mine and for others. I do have the Platinum version of all the Waves plugins to help. I think it would be nearly impossible to do a decent job of mastering with the stock plugins that come with PTLE.

However, you can use just about any program for the final EQ and compression tweaking. It don't think Protools has any particular advantage there. I also use the latest version of Toast (which includes the older version of Jam as well). The monitoring environment and good ears are really the key to getting well-mastered CD projects much more so than what software you would use.

I do think there are programs that make it easier to get consistent results (final CD layout) with the pauses, levels, crossfades, etc than Protools. For instance, Waveburner, which comes with Logic Pro is a mastering program that makes track layout pretty easy. Also, check out Peak Pro, which is a Mac-based mastering program.