I was tempted by the Singular Kite, as the team I used to race for was sponsored by Paul Sadoff at Rock Lobster so I've a passion for steel. I've also owned a Bontrager CX and a Salsa Cross before that.
However, that was the 90's and having got back into CX last season I bought a cheap Kona Jake, which was a basic but nice enough frame until I tried a Jake the Snake (Easton Ultrawall) and was immediately impressed with the difference, so replaced the Jake with that. Then hankered after steel again so bought a Cotic, which as soon as I built and rode it I realised was not a CX bike but a mountain bike masquerading as a CX bike and had too many quirks for my taste, so sold all of that and was flip-flopping between the Singular Kite and a Specialized Crux.
What sold me on the Crux was I went to watch the Rapha Supercross at Alexandra Palace - where last year's UK National CX Champion was on a Crux as were several of the top pros. I got talking to some of them and said "Hey, that's a pretty cheap frame, how does it ride?" Their responses were unanimous - very, very good. The frame is waaaay better than the components Specialized hang on it when sold as a complete bike and warrants much higher end kit. The frame is an Elite level race frame.
So I bought a Cruz frameset and hung a mixture of SRAM Red/Force gruppo on it, with handbuilt clincher wheelset (Hope hubs/Velocity A23 rims) etc.
I rode it for 4+ hours at last weekend's Salisbury CX Sportive which was it's maiden voyage and have done two 1-2hrs road rides since and love it. It fits well, is made well, is very, very light (frame approx 1,500g) whole bike is 18lbs without spending silly money and it's rippingly fast. Right now, I can think of no downsides.
I'm sure in time I will cave in and also buy a Singular Kite or similar just so that I have a steel frame back in my armoury but for now I'm really liking the Crux.
The fact that several national champions ride them (UK, USA, etc) speaks volumes too. It's not just that they're sponsored - when you see how fast they ride those things you realise that the frame itself certainly isn't a limiting factor for mere mortals like us.