Aside from the novelty in it being a collector's item, the only suitable purpose for this shotgun is home defense. Shotgun sports, competition, and hunting would be very impractical.
If you already own a one or two dependable shotguns, and want something unique, by all means get a SPAS 12. It's an excellent conversation piece. However in terms of performance versus modern semi-automatic shotguns, it's reliability with light loads, weight, and lack of spare parts make it a poor choice for practical use.
I always tell people that it's the DeLorean of the shotgun world. Visually impressive and unique, with some interesting features. However, poor performance and (now) lack of parts availability limit it to range toy and safe queen.