I had a great experience with this! I booked a solo hike with the Besakih route. I knew I would be slow, so I messaged the company and requested to start the hike earlier, so I'd be able to make it for sunrise and they were totally fine with it. It was a tough hike for me, but I managed to reach there right at sunrise and was able to enjoy the amazing views and my guide was very great and supportive the whole way.
My driver Gusti was really accommodating and nice, I requested a different drop-off from my pick-up point, and he let me leave my luggage in the car overnight, so I would be able to go straight to my next destination.
Probably the best and most challenging thing I've done so far in Bali, I highly recommend it if you enjoy hiking, but note that it is really slippery going down on the loose soil and rocks, so it would be best if you wear proper footwear.