I own a Ibanez Prestige 7-String (no 8, but the “problems” are the same). It´s a little bit harder to play, the Neck is a flatter and the fretboard wider, muting is harder. If you hands are small, extended range could be a problem, because of the wider Fretboard
If you want to test it, go to your local guitar dealer and check out a 7string.
Some points that are difficult to:
– coordination around the fretboard – even one string more can be confusing
– Simple tunings like drop d aren´t makeable
What helped me about this (mind setting): It´s just a 6-String with some extra low range.
I hope, that my thoughts on this may help you!