I have a Squier Vintage Modified Jazz Bass Fretless - check it out at the link below. These basses are excellent ... virtually perfect and better made and finished than the Fender MIM basses I have seen. I only changed the bridge to a more substantial Gotoh which is similar to a Badass (but cheaper!). The bass comes with Seymour Duncan designed pickups (cheaper version of the real thing) but they are super sounding. The fretboard has thin white lines and is made of ebonol which is almost like bakelite - smooth as hell and very hard.
Something you have to bear in mind is that most fretless players try and emulate the Jaco sound - that means tone backed off on the bass, rear pickup volume flat out, amp bass and low mids turned up. The rest is in your hands ... err .. fingers ... you got to make it sing! And you have to play ON the line, not behind it as with fretted basses. Also the idea is to almost use the hand vibrato technique to "feel" you way onto the note ... that is part of the fretless way of life!
I may just part with mine as I have just got a third 6-string bass and harldy play the fretless.
http://www.muz.co.za/index.php?main_page=product_info&cPath=91_92&products_id=2266