I finished my XM install last night. Certainly a ripoff for anything more than $100. It looks difficult, but really only takes about 1 hr if the installer has done one before.
As far as sound quality goes, I'm satisfied, but the volume isn't great. Toyota/Lexus should have worked harder to get the volume to better match that of AM/FM/CD as I always find myself turning the XM volume way up then back down when I switch to the other inputs. I have the same problem in my IS350, so it's not just the T4R.
I left everything apart since I'll be installing the Parrot Kit tonight. Found the mute wire on the JBL 10 speaker Synthesis with no problem (F7 Red/White wire). Will tap into the center speaker for the voice from the Parrot so it will all sound factory. Eight wires to connect, mount the Parrot somewhere and I'm done.