I've played the same Shifter twice (in the same store). I keep going back to it. I really like it a lot!
It does sound different than a typical Jazz Bass. It also has more distinct tones than a passive Jazz, too. But, they are all definitely different. The switching scheme is not very intuitive- the push/pull pot and wiring order seemed strange to me. But, the tones were all very good! Oddly, one of the dual-pup settings was just as noise prone as the single pup settings. Odd. There are unique & very usable tones in the Shifter.
The neck, while narrow, does not feel like a Jazz. It is deeper and more conical overall. It fits my hands nicely - but I'm very adaptable as far as ergonomics and have very long fingers. YMMV. The bass felt comfy & looked absolutely killer in yellow/white!
Honestly, I don't see the Shifter as a desert-island, only one bass instrument. It is a great complement, though , if you already have the 'classic' tones covered & are looking for something different, but usable.
So, definitely not a Jazz Bass substitute, but definitely a worthwhile bass to check out! I really want one (just trying to justify the purchase!).