Hi Owen,
I've been a Sire Fretless player for a week and a day (at the time of writing). Mine is a 4 string V7 Alder in the Antique White. It looks very cool with the coated ebony fingerboard, red pickguard (and, if you choose to wear them, a black shirt, red tie, white trousers and maybe some black and white ska braces). The neck is very quick to get round (though calling me quick in any situation would probably be stretching reality a bit), but I suspect this is more to do with the satin jazz neck and flatwound strings than the coated fingerboard. The rolled edges probably make it a bit more comfortable when moving quickly.
After reading your post I played it to see if I was actually touching the fingerboard. I think my little finger did occasionally, but I think most of the time fingers are on strings or hovering just above them rather than in contact with the fingerboard. (Edit a couple of days later: no finger contact with the fingerboard on the E string, hardly any on the A, a bit on the D and in contact on the G between the intonating finger and the fingerboard edge). So I think the coating is more to do with aesthetics and giving the wood some protection from contact with strings.
The only other fretless I played was an Ibanez in the £350 - £400 range, with (I think) an uncoated fingerboard; it had a narrow width neck and maybe a slimmer profile than the Sire (note "maybe"). It was nice to play though and put a smile on my face. Bearing in mind that it was 6 weeks or so ago that I played it, my impression is that the Sire is quicker. I suspect what I really mean is that the Sire has less friction due to the flatwounds (thus giving the impression of being quick) vs the Ibanez which had roundwounds (and thus probably more friction).
Bottom line: the Sire is really nice to play. The coated fingerboard looks really cool, but I suspect the neck and flatwound strings have more influence on how it feels to play.
I hope this helps.
Cheers,
Simon