It keeps drying out on me. I'm thinking of gluing some aluminum foil to the top.
In all seriousness, though, I would like to get a mobile in my car as well (Kenwood TM-V71A looks pretty sweet). So I'm eagerly awaiting some recommendations for the OP as well.
I had a Palmetto Antenna before that was very good...this one is WAY Better...all the dead spots I had before on my way into work are gone now...and I can reach much further with this one.