Personally, I'm in love with my Vengeance Demon Hunter. I leveled him to 101 through questing when the expansion first came out and I left him there for quite a while. I found out about 101 twinking and lucky for me, I had him sitting there and ready to go! I bought a bunch of BoE's (which were like 5-10k a piece at the time), decked him out and got to work wrecking stuff. Now that I have a very strong understanding of the class and spec, I can do some pretty crazy things.
In world PvP I can't necessarily kill 110's incredibly fast like some twinks, but I can sure knock them down over time while being nearly unkillable. The self healing on Vengeance Demon Hunters is incredible, even with 0 leech. I can easily sit at less than half health and go to full with one Soul Cleave that consumes 1-2 Soul Fragments.
In dungeons is where I have the most fun, I was a big fan of WoW Hobbs back in the day and I LOVED his big pull videos. There's just something about pulling nearly the whole dungeon and beginning to AoE them down... those numbers cluttering your screen... procs left and right... it's so satisfying! Just an example: I do Halls of Valor in 3 pulls, all trash from the entrance + Hymdall > all trash past Hymdall + all trash in the Hearth of Revelry + all trash up to and including the two mini bosses before Hyrja > most trash within Field of the Eternal Hunt + Fenryr > then of course finishing the rest of the fights regularly.
I've been thinking about making a video for each dungeon and some other content (if anyone would want to watch, lol), I do stream casually too when I'm doing things like power leveling runs, etc. Overall, I've enjoyed the experience I've had with my Demon Hunter and I'd give a solid "8/8 would r8 gr8 m8"!