It's very good up to a point. I tried doing a quote, and found that you have to specify every single bicycle regardless of value. That's a pain for me, as I have lots, most of which aren't actually worth over £1000 (which is their limit for specifying anything else). A fair jump in price for specifying the first expensive bike, but pleasingly it didn't go up much more when I added a couple more. Until that is I started adding in the <£1000 bikes and went over £10,000 of bikes in total, at which point the premium jumped from ~£300 to >£1000. If you have less than £10,000 total of bikes I think it's probably the best value you can get (obviously that depends on your location etc. - it's good for me). However I'd have to think carefully about whether it was worth having several less expensive (but still >£500) bikes uninsured.
I'd also be having an interesting conversation as it asks you to specify bicycles, but the dropdown category is "cycles" and I have a unicycle which would cost more than £1000 to replace (I only paid £300, but I've never even seen another one come up s/h for anywhere near that price). Given the apparent £10k limit it is of course possible I've already had that conversation as I tried to get a quote from somebody who wanted me to specify all cycles and may have had a £10k limit.