I'm pretty much 95% fretless for the last 7 or so years. I love fretless, I love the sound, the feel and everything about it. There are a few things that you can't do on fretless like slap, well you can do it but it sounds different and it kind of marks up your fretboard a bit but other then that it's all good. I have 2 Warwick fretless basses as you can see and an old Gibson G3 4 string that's been all reworked. In my opinion, and I've said it before on different posts, there is no better sounding fretless bass then a Warwick Thumb. BO or neck through, there is no bass that's got that sound. I get so many compliments from people on the sound. I've practiced a lot with it too and my suggestion is that you leave your fretted bass at home for about 6 months and just play fretless, you will develop your sound and your intonation will get pretty good too. And finally, save your money and buy a Warwick fretless, you'll never regret it.
Rock on my friend.
LR