I'll start off by saying that I have not seen or used one in person, but they're probably my second favorite saber SF makes (visually) besides my Prodigal Son (and maybe the Exhalted, love the thin necks).
With that being said... I've heard they're not very comfortable for spinning at all, and most use it mainly for display and cosplay. I believe the bottom of the hilt has 4 long, thin metal grip pieces that are usually thicker plastic (or rubber?) grips on regular starkiller hilts. I've read these are a bit uncomfortable, but they do not look removable from the body.
Then of course on the upper part of the hilt you have the revealed crystal chamber, which looks badass, but is probably not a great area for gripping and spinning consistently either.
All in all its a favorite for a lot of people here to look at, but the design would benefit from a more comfortable handle. I don't duel really, so if and when I get a 2nd saber, most likely that would be it for me along with a thin-walled blade from somewhere else for less heavy cosplay.