I swapped to one last year, and found it brilliant to use up wind, it does require a different approach at the top mark when bearing off, and reaching, but upwind in a blow, especially when gusty, brilliant…. I didn’t have to sit up to create the angle to release the main sheet…some will now suggest I don’t lean out, but just occasionally there are “double cheek” days!!
Justin
The Flying Fifteen Blog 
The spinlock cleats are quite good also, mounts the traditional way up and is a two finger release in any wind strength
Can’t just leave it like that Justin ! What’s the technique on a reach then?
As an aside I’ve just fitted a Sprenger Jammer on my laser 2000, fantastic quality, (they’ve done quality horse tack for years), up there with Harken with the facility to mount the cleat underneath as described. http://www.ebay.co.uk/itm/New-Mainsheet-Swivel-Jammer-High-Arm-Sailing-Dinghy-Yacht-Wayfarer-Fireball-Lark-/130799160054?pt=UK_Sporting_Goods_Sailing&hash=item1e743ccaf6
I think one problem is that the main sheet jammer on most Fifteens is too high, sat on top of a silly console!! But let’s not go back on that one !!
Ian.