I had one of the original Lefty forks on my hardtail from 2000. Indeed that bike is still in my shed and occasionally gets ridden. For all that it looks like it should handle and feel really different, then in reality it doesn't, at least not in the way you think it should. Just like the crankset / chain / cassette being on only the right side of the bike, you don't notice any lean which a lot of people think you would. There was also the assumption that the fork was a bit more flexy than the traditional two sided. And this is the difference, it was way way stiffer than any other fork of similar weight at the time (Rockshock SID I'm talking to you you spineless lump of cooked spaghetti). And it had a lot less stiction than others too.
Where it suffered was in the ability to get it serviced (in the UK at least), and probably the development didn't keep up with other shocks in the tenability - Cannondale's R&D budget spread over many components, RockShox etc had just one thing to focus on.
But, I do worry about just how many bikes we're supposed to have. Used to be Road and MTB. Then it was Downhill, Cross country and Road. Add in Commute, Cyclocross, All country MTB, Enduro, then I think we've got everything from rigid through to 160mm in 10mm increments of travel. I have to say that for me, I'm 'covered' with cyclocross and Spec Epic overlapping where a suspension gravel bike would fall.
I regret not patenting it. But back in 1990 when I was a teenager, I didn't have one of the new fangled mountain bikes all the rich kids were getting. I just had my old Ameco road bike. But I lived in the country and surrounded by bridleways, or horse/ walking trails if you don't know what they are. And so I'd go off on those trails ignoring any concern for tyres, wheels or frame strength. And it never broke. Jump to more recent times, and there's plenty of routes we do here where we have had stretches of gravel. Sure I wouldn't use zipp carbon rim climbing wheels on my club training rides if we were going gravel, but the 10 year old 101s have never needed truing, and I've never had a puncture when gravel riding on standard road tyres.
But I'm glad that Cannondale is out there. As if it gets someone out doing the type of riding they enjoy, and I enjoy - just go out and ride, don't be afraid to explore that new turn you've never gone down, then that's brilliant.