I got the Sirius radio for my gf at christmas, she drives a 2000 TJ.
I put the antennae on the front windshield wiper cowl, right in front of the driver's side. I also used the suction cup window mount, but I'm going to design a little console for the inside for it... Not many places for the thing to fit really in the cab that I know of. Pretty easy to install the thing.
There's a signal indicator for satellite and what I think is land towers/antennas (terra). I could pick up a signal with the antennae on top of the speaker box, under the soft top, but the signal was somewhat weak, but there for sure.
Now if you care about such things, Sirius is going to have Howard Stern, not XM. I don't listen to him anyways but she says she does.
It's pretty cool though, great not to have commercials but there's the occasional station identification, only lasts a couple seconds tho.
Troy