Love my Nav, no regrets whatsoever.
I do use the GPS often since I've been doing a lot of travel to unfamiliar places
these past couple of years and the voice + bluetooth integration is great.
They passed a law in Maryland not long ago that made handsfree mandatory, although everyone pretty much ignores it and still uses their handsets, which pisses me off
because I wind up getting cut off frequently by unattentive people yapping on their phones in their Escalades , but that's another story.
On the other hand, I've never used the music box (I have my iPod that I've already ripped all my CDs to). Come to think of it, I don't think I've ever used the CD player either
. I mostly just use the XM, FM, and iPod.
I'd say go with it if you want its features. Gives the interior that nice finished (sort of luxary) touch.