I saw that the MP3 activation price was cut to $10, so I'm considering just finally activating it once and for all. I've never actually used the built in encoder, (always had LAME in the past with ok results), and was wondering if it had any features (e.g. tag editing, easy bit-rate setting, etc..), that are different or better than what the LAME driver offers.

It is a convenience feature, providing a subset of the LAME command line arguments in a dialog integrated into SONAR.

OK cool that's exactly what I was wanting to know, I'm ok with $10 to be convenienced I think!

It feels like it was quickly developed a long time ago, and not updated since.  But it gets the job done, with manual tagging, for static rate mp3s. 
 
There are issues using it for variable bit rate:  the time of the resulting file is way out of whack (e.g. a 3 minute mp3 will appear as over 8 minutes).

If you do elect to activate the integrated encoder, you can update the bundled encoder with the libraries in this thread.

Thanks for reminding me, my 64 bit lame.exe file was rather old so just updated it to 3.99.2.5

scook
If you do elect to activate the integrated encoder, you can update the bundled encoder with the libraries in this thread.

Is that newer than what's in X3, really? Just cause it seems to be from '09?

Yes. That is true too.

I got mine here but this isn't the official source:
http://www.rarewares.org/mp3-lame-bundle.php
 

So we could use those with the same instructions?
I just picked it up for ten bucks too. Figure at ten cents per file, it'll still pay for itself in a month or two :)