Multi speed fixed is something that has expanded my love of and relative usefulness of my fixed gear bikes and experience.
Owner of a dingle and the S3X hub, they both have some usefulness and drawbacks.
Dingle: I personally use with a single chainring, though have been contemplating a double upfront. Currently have 17/20 which gives me 72 and 61 GI respectively. With 9 speed chain, chainline is not an issue. Not rubbing or jumping. Plan to play around with gearing come spring. Nice to ride out to local trail, change to lower gearing for gravel and hillier sections, then change back for ride home.
S3X: similar to
JohnDThompson and his experience. I have 1200-1500+ miles on it at this point, and it has been trouble free for the most part. Ability to change gears with a shifter is fantastic. Although, it's by FAR my heaviest fixed gear I'm consistently faster because of ability to be in a less wrong gear more frequently. Currently at approx 91, 68.5, and 57 gear inches. When riding with roadies I use this bike because it helps reduce rubber banding effect. I can spin out on middle gearing but have the larger gearing to keep up on downhills or when hammering. I also gear down for winter and ride something like 69, 52, 43. This would also be my preferred off-road gearing or near about. And similar to Mr Thompson, I wish the gearing was closer to the ASC. Doesn't have the traditional fixed gear feel, but it's certainly a fixed gear. I paid $199 shipped from bike island for complete wheelset with shifters, etc. Absurdly heavy, but bulletproof. Would buy again without hesitation.
I still lust after, and look for ASC hubs for a future build. But I am satisfied with having multiple fixed gear experiences. Debating the practicality of fixed gear is interesting, because it's rarely practical. I'm almost always in the wrong gear anyway.