I've got an ancient 1×1. It's a nice bike. I doubt I'll ever part with it, the frame is too tatty to be worth anything, but it keeps being too useful even though I have switched to 29ers now.
I have used it for a Euro SS champs and 2 'Puffers and taken it as a backup for other races. Nice handling and predictable. Soaks up a lot of punishment and has no nasty habits that will bring you down when you're knackered and stupid on an icy descent at 3am.
It's steel so it's about a lb heavier than an alloy bike when built up. I prefer it with a carbon fork to suspension.
I'll have it at the next 'Puffer setup with drum brakes for a mudfest – the big clearances mean it's ideal for that. I've finally managed to get my hands on a set of ice tyres for my 29er, so I'll be riding that if it's icy.