Cyclists love OSM (and OSM loves cyclists).
An anonymous happy cyclist has uploaded their tracks of National Cycle Route 8, Lon Las Cymru - the Welsh national route from Cardiff to Holyhead. I cycled this a few years back, but without GPS (I only had a yellow eTrex at the time, and the memory would have filled up too quickly), so had mapped what I could remember from NPE - in fact, wanting to do this was the initial reason I added NPE to Potlatch. Over time I've been refining it whenever I've revisited an area (Brecon last weekend, Cardiff a month or two ago) but there were still some gaps.
The mystery cyclist's GPS track has meant that it's now almost entirely complete. Only a small bit in Llanfairpwyngwyngyll (etc.) remains to be done, plus two alternative braids which we might cycle this Easter.
Thank you mystery cyclist, whoever you are.