The purpose to a longer scale length is to take advantage of thinner gauges to tune in a traditional manner IMO.
The benefit is more articulation across the spectrum, and better, more consistent response across the fret board. The very low end benefits most as it allows thes strings to come into closer tension proximity to standard treble tensions.
Playability has everything to do with how the designer created the instrument - if the bass was created by taking a standard 34" scale bass and tacking on the additional length to the neck purely I am betting you won't care for the way it feels.
The overal length needs to be extended forward and back in order for the bass to feel comfortable when it is played, and the best indicator of this is where the upper horn/bout and the associated strap button falls in relation to the 12th fret. Just shy, but very close to it indicates the length was pushed out in both directions and that the 'reach' will be minimal. It will also sit well on your body and not dive.
