I got some new pics of my setup. The picture shows the XM MyFi with a new cover that now matches the woodgrain in the dash. I have it mounted on an E90 specific Kuda mount. The wires are hidden under the mount and run along the inside edge of the center console. The antenna wire continues under the passenger seat up to the corner of the back window along the inside edge of the trim. I used double sided tape to hold the actual antenna in position and out of site (for the most part).
The reason I went with this setup is because I like to prerecord music on the Myfi so I can skip past songs I do not want to hear. Also, I can just plug it into a lighter outlet for power (if needed for a long trip). Usually, I just run it off the battery. However, I bought a Cigarette Lighter Splitter Adaptor
so I can plug in my cellphone and XM on long trips. I just slide the thing between the passenger seat and the console.
The other cool thing about the Myfi is that I can take it into work and play it back there just using the internal antenna and the FM freq on my radio. I usually plug it into an electrical outlet at that time to keep it charged up.