Right, there is a Gscript for that. Start Gscript, menu->load file, and there should be one called something like remove_peep.sh. Run that script just like you ran the rooting process (except, in this case, you need that check box "Need SU?" checked.)
Overclocked/underclocked: The Eris, when running stock software, runs the CPU at 528 MHz. Using some clever tricks, the actual CPU speed can be set to be as slow as 19.2 MHz and as high as somewhere over 800 MHz. For most Erises, 710 MHz is a stable maximum speed - the phone will continue to run without having the CPU stop running from overheating.
Most rooted ROMs, including xtrSENSE, run the CPU in a series of stepped speeds from as low as 245 MHz (when your phone is idle, doing nothing, and particularly when the display is turned off) and, as processor demand increases - as you do more with your phone - the speed will step up to as high as 710 MHz. This makes the phone both feel faster when you use it, and burn less power when it is sitting idle, as the slower clock speeds draw less voltage from the battery.
One other thing that I noticed about xtrSENSE in the change log is that the Amazon MP3 store is removed by default, since it is available in the market if you really want it.
I think I explained the cache2cache as well as I could. Basically, as your apps run, their code and data are cached in special files that run faster than interpreting the code as the application runs, and these caches are moved to a different location in your phone in xtrSENSE, leaving the space for applications and their data far larger.
Wired and wireless tethering apps should be well understood - basically, they let you share your 3G data with a computer connected by cable, or connected by WiFi, if you are out and about with a computer with no other WiFi data source. You, of course, have absolutely little interest in this feature, if you have a severely limited data plan with PagePlus. Verizon Wireless customers with unlimited data plans may be more interested in that feature, though.