So, my boat has a self-tacking 100% jib using a track. It's great for short-tacking to windward up the estuary and lazy sailing days. Between that and the power winches the crew is getting positively lazy.
There are some downsides, most notably when heading dead downwind in light breezes. We usually just give up and roll up the jib under those circumstances since the flapping back and forth getting pretty anoying very quickly. I also think tacks are a bit slower since you can't back the jib to help the bow go across. And heaving-to means going forward to set a pinstop to keep the jib backed.
All in all though, for short-handed sailing its great.
Yare - Morris M36 #50